Multivalent pneumococcal polysaccharide-protein conjugate composition

ABSTRACT

An immunogenic composition having 13 distinct polysaccharide-protein conjugates and optionally, an aluminum-based adjuvant, is described. Each conjugate contains a capsular polysaccharide prepared from a different serotype of  Streptococcus pneumoniae  (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F) conjugated to a carrier protein. The immunogenic composition, formulated as a vaccine, increases coverage against pneumococcal disease in infants and young children globally, and provides coverage for serotypes 6A and 19A that is not dependent on the limitations of serogroup cross-protection. Also described is a method for making an immunogenic conjugate comprising  Streptococcus pneumoniae  serotype 3 polysaccharide covalently linked to a carrier protein, the method including periodic acid oxidation of the polysaccharide in the presence of bivalent cations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 11/395,593, filed Mar. 31, 2006, which claims the benefit of U.S. Provisional Application No. 60/669,605, filed Apr. 8, 2005, each of which is hereby incorporated in its entirety by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to the field of medicine, and specifically to microbiology, immunology, vaccines and the prevention of infection by a bacterial pathogen by immunization.

BACKGROUND OF THE INVENTION

Streptococcus pneumoniae is a leading cause of meningitis, pneumonia, and severe invasive disease in infants and young children throughout the world. The multivalent pneumococcal polysaccharide vaccines have been licensed for many years and have proved valuable in preventing pneumococcal disease in elderly adults and high-risk patients. However, infants and young children respond poorly to most pneumococcal polysaccharides. The 7-valent pneumococcal conjugate vaccine (7vPnC, Prevnar®) was the first of its kind demonstrated to be highly immunogenic and effective against invasive disease and otitis media in infants and young children. This vaccine is now approved in many countries around the world. Prevnar contains the capsular polysaccharides from serotypes 4, 6B, 9V, 14, 18C, 19F and 23F, each conjugated to a carrier protein designated CRM₁₉₇. Prevnar covers approximately 80-90%, 60-80%, and 40-80% of invasive pneumococcal disease (IPD) in the US, Europe, and other regions of the world, respectively [1, 2]. Surveillance data gathered in the years following Prevnar's introduction has clearly demonstrated a reduction of invasive pneumococcal disease in US infants as expected (FIG. 1) [3, 4].

Surveillance of IPD conducted in US infants prior to the introduction of Prevnar demonstrated that a significant portion of disease due to serogroups 6 and 19 was due to the 6A (approximately one-third) and 19A (approximately one-fourth) serotypes [5, 6]. Pneumococcal invasive disease surveillance conducted in the US after licensure of Prevnar suggests that a large burden of disease is still attributable to serotypes 6A and 19A (FIG. 1) [3]. Moreover, these two serotypes account for more cases of invasive disease than serotypes 1, 3, 5, and 7F combined (8.2 vs. 3.3 cases/100,000 children 2 years and under). In addition, serotypes 6A and 19A are associated with high rates of antibiotic resistance (FIG. 2) [7, 8, 9]. While it is possible that serogroup cross-protection will result in a decline of serotype 6A and 19A disease as more children are immunized, there is evidence to suggest that there will be a limit to the decline, and a significant burden of disease due to these serotypes will remain (see below).

Given the relative burden and importance of invasive pneumococcal disease due to serotypes 1, 3, 5, 6A, 7F, and 19A, adding these serotypes to the Prevnar formulation would increase coverage for invasive disease to >90% in the US and Europe, and as high as 70%-80% in Asia and Latin America. This vaccine would significantly expand coverage beyond that of Prevnar, and provide coverage for 6A and 19A that is not dependent on the limitations of serogroup cross-protection.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides generally a multivalent immunogenic composition comprising 13 distinct polysaccharide-protein conjugates, wherein each of the conjugates contains a capsular polysaccharide from a different serotype of Streptococcus pneumoniae conjugated to a carrier protein, together with a physiologically acceptable vehicle. Optionally, an adjuvant, such as an aluminum-based adjuvant, is included in the formulation. More specifically, the present invention provides a 13-valent pneumococcal conjugate (13vPnC) composition comprising the seven serotypes in the 7vPnC vaccine (4, 6B, 9V, 14, 18C, 19F and 23F) plus six additional serotypes (1, 3, 5, 6A, 7F and 19A).

The present invention also provides a multivalent immunogenic composition, wherein the capsular polysaccharides are from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F of Streptococcus pneumoniae and the carrier protein is CRM₁₉₇.

The present invention further provides a multivalent immunogenic composition, wherein the capsular polysaccharides are from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F of Streptococcus pneumoniae, the carrier protein is CRM₁₉₇, and the adjuvant is an aluminum-based adjuvant, such as aluminum phosphate, aluminum sulfate and aluminum hydroxide. In a particular embodiment of the invention, the adjuvant is aluminum phosphate.

The present invention also provides a multivalent immunogenic composition, comprising polysaccharide-protein conjugates together with a physiologically acceptable vehicle, wherein each of the conjugates comprises a capsular polysaccharide from a different serotype of Streptococcus pneumoniae conjugated to a carrier protein, and the capsular polysaccharides are prepared from serotype 3 and at least one additional serotype.

In one embodiment of this multivalent immunogenic composition, the additional serotype is selected from the group consisting of serotypes 1, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F. In another embodiment, the carrier protein is CRM₁₉₇. In yet another embodiment, the composition comprises an adjuvant, such as an aluminum-based adjuvant selected from aluminum phosphate, aluminum sulfate and aluminum hydroxide. In a particular embodiment, the adjuvant is aluminum phosphate.

The present invention also provides a multivalent immunogenic composition, comprising polysaccharide-protein conjugates together with a physiologically acceptable vehicle, wherein each of the conjugates comprises a capsular polysaccharide from a different serotype of Streptococcus pneumoniae conjugated to a carrier protein, and the capsular polysaccharides are prepared from serotypes 4, 6B, 9V, 14, 18C, 19F, 23F and at least one additional serotype.

In one embodiment of this multivalent immunogenic composition, the additional serotype is selected from the group consisting of serotypes 1, 3, 5, 6A, 7F, and 19A. In another embodiment, the carrier protein is CRM₁₉₇. In yet another embodiment, the composition comprises an adjuvant, such as an aluminum-based adjuvant selected from aluminum phosphate, aluminum sulfate and aluminum hydroxide. In a particular embodiment, the adjuvant is aluminum phosphate.

The present invention also provides a method of inducing an immune response to a Streptococcus pneumoniae capsular polysaccharide conjugate, comprising administering to a human an immunologically effective amount of any of the immunogenic compositions just described.

The present invention further provides that any of the immunogenic compositions administered is a single 0.5 mL dose formulated to contain: 2 μg of each saccharide, except for 6B at 4 μg; approximately 29 μg CRM₁₉₇ carrier protein; 0.125 mg of elemental aluminum (0.5 mg aluminum phosphate) adjuvant; and sodium chloride and sodium succinate buffer as excipients.

Methods for making an immunogenic conjugate comprising Streptococcus pneumoniae serotype 3 (Pn 3) polysaccharide covalently linked to a carrier protein are also provided. In one embodiment, the method comprises (i) reacting purified Pn 3 polysaccharide with a mild acid resulting in a hydrolyzed Pn 3 polysaccharide; (ii) reacting the hydrolyzed Pn 3 polysaccharide with an oxidizing agent in the presence of bivalent cations resulting in an activated Pn 3 polysaccharide; (iii) compounding the activated Pn 3 polysaccharide with a carrier protein; (iv) reacting the compounded, activated Pn 3 polysaccharide and carrier protein with a reducing agent resulting in a Pn 3 polysaccharide:carrier protein conjugate; and (v) capping unreacted aldehydes in the Pn 3 polysaccharide:carrier protein conjugate resulting in an immunogenic conjugate comprising Streptococcus pneumoniae Pn 3 polysaccharide covalently linked to a carrier protein.

In a further embodiment, the method comprises (i) reacting purified Pn 3 polysaccharide with acetic acid resulting in a hydrolyzed Pn 3 polysaccharide; (ii) reacting the hydrolyzed Pn 3 polysaccharide with periodic acid in the presence of MgCl₂ resulting in an activated Pn 3 polysaccharide; (iii) purifying the activated Pn 3 polysaccharide; (iv) compounding the activated Pn 3 polysaccharide with a carrier protein; (v) co-lyophilizing the compounded, activated Pn 3 polysaccharide and carrier protein; (vi) reacting the co-lyophilized, activated Pn 3 polysaccharide and carrier protein with sodium cyanoborohydride resulting in a Pn 3 polysaccharide:carrier protein conjugate; and (vii) capping unreacted aldehydes in the Pn 3 polysaccharide:carrier protein conjugate with sodium borohydride resulting in an immunogenic conjugate comprising Streptococcus pneumoniae Pn 3 polysaccharide covalently linked to a carrier protein.

A method for making an activated Streptococcus pneumoniae Pn 3 polysaccharide is also provided. The method comprises (i) reacting purified Pn 3 polysaccharide with a mild acid resulting in a hydrolyzed Pn 3 polysaccharide; and (ii) reacting the hydrolyzed Pn 3 polysaccharide with an oxidizing agent in the presence of bivalent cations resulting in an activated Pn 3 polysaccharide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the changes in IPD rates by serotype in US children <2 years of age from baseline (1998/1999) to 2001.

FIG. 2 depicts the distribution of pneumococcal isolates with resistance to penicillin (PCN) in children <5 years of age (1998).

FIG. 3 depicts the reverse cumulative distribution curves (RCDC) of OPA post-third dose results from the D118-P16 Prevnar trial.

DETAILED DESCRIPTION OF THE INVENTION

Inclusion of Prevnar Serotypes 4, 6B, 9V, 14, 18C, 19F, 23F

Data from IPD surveillance between 1995-1998 estimated that the seven serotypes in Prevnar were responsible for around 82% of IPD in children <2 years of age [5]. In Northern California, the site of the efficacy trial, the Prevnar serotypes accounted for 90% of all cases of IPD in infants and young children [10]. Since introduction of the Prevnar vaccine in 2000, there has been a significant decrease in the overall IPD rates due to a decrease in disease due to the vaccine serotypes [3, 4]. Therefore, there is no justification at this time to remove any of the Prevnar serotypes from the next generation of pneumococcal conjugate vaccines but rather to add serotypes to obtain wider coverage.

Inclusion of Serotypes 1, 3, 5 and 7F

In the US, the rate of IPD caused by serotype 1 in children under the age of 5 years is <2%, about the same as for each of types 3 and 7F [1, 6]. Serotypes 1 and 5 account for higher rates of IPD in US populations at high risk for invasive pneumococcal disease. Specifically, serotype 1 causes 3.5% of IPD in Alaskan native children <2 years of age, and 18% in children 2-4 years of age [11]. Both serotype 1 and serotype 5 significantly cause disease in other parts of the world and in indigenous populations in developed countries [12, 13, 14].

Serotype 1 may also be associated with more severe disease as compared with other pneumococcal serotypes [15]. This observation is based on the difference in rates of case identification between the US and Europe, and the associated difference in medical practice. Overall, the incidence of IPD is lower in Europe than in the US. However, the percent of IPD caused by serotype 1 in Europe is disproportionately higher than in the US (6-7%, vs. 1-2%, respectively). In Europe, blood cultures are obtained predominantly from hospitalized children. In the US, it is routine medical practice to obtain blood cultures in an outpatient setting from children presenting with fever ≧39° C. and elevated white blood cell counts. Given the difference in medical practice, it is postulated that the lower percent of disease caused by serotype 1 in the US may be diluted by higher rates of other serotypes causing milder disease, while the higher percent in Europe reflects more serious disease. In addition, seroepidemiology studies of children with complicated pneumonia demonstrate that serotype 1 is disproportionately represented [16, 17, 18]. This suggests that inclusion of serotype 1 may reduce the amount of severe pneumococcal disease, as well as, contribute to a total reduction in invasive pneumococcal disease.

The addition of serotypes 3 and 7F will increase coverage against IPD in most areas of the world by approximately 3%-7%, and in Asia by around 9%. Thus, an 11-valent vaccine would cover 50% in Asia and around 80% of IPD in all other regions [1, 2]. These serotypes are also important with respect to otitis media coverage [19]. In a multinational study of pneumococcal serotypes causing otitis media, Hausdorff et al. found serotype 3 to be the 8th most common middle ear fluid isolate overall [20]. Serotype 3 accounted for up to 8.7% of pneumococcal serotypes associated with otitis media. Thus, the importance of types 3 and 7F in otitis media, as well as in IPD, warrants their inclusion in a pneumococcal conjugate vaccine.

However, attempts to produce a multivalent pneumococcal conjugate vaccine that exhibits significant immunogenicity with respect to serotype 3 polysaccharides have been unsuccessful. For example, in a study of the immunogenicity and safety of an 11-valent pneumococcal protein D conjugate vaccine (11-Pn-PD), no priming effect was observed for serotype 3 in infants who had received three doses of the vaccine followed by a booster dose of either the same vaccine or a pneumococcal polysaccharide vaccine (Nurkka et al. (2004) Ped. Inf. Dis. J., 23:1008-1014). In another study, opsonophagocytic assay (OPA) results from infants who had received doses of 11-Pn-PD failed to show antibody responses for serotype 3 at levels comparable to other tested serotypes (Gatchalian et al., 17^(th) Annual Meeting of the Eur. Soc. Paed. Inf. Dis. (ESPID), Poster No. 4, P1A Poster Session 1, Istanbul Turkey, Mar. 27, 2001). In yet another study, which assessed the efficacy of an 11-Pn-PD in the prevention of acute otitis media, the vaccine did not provide protection against episodes caused by serotype 3 (Prymula et al. (2006) Lancet, 367:740-748). Accordingly, a pneumococcal conjugate vaccine comprising capsular polysaccharides from serotype 3 and capable of eliciting an immunogenic response to serotype 3 polysaccharides provides a significant improvement over the existing state of the art.

Inclusion of Serotypes 6A and 19A

a. Epidemiology of Serotypes 6A and 19A

Surveillance data in the literature suggest that serotypes 6A and 19A account for more invasive pneumococcal disease in US children <2 years of age than serotypes 1, 3, 5, and 7F combined (FIG. 1) [1, 5]. In addition, these serotypes are commonly associated with antibiotic resistance (FIG. 2) and play an important role in otitis media[6, 19, 20]. The ability of the current Prevnar vaccine to protect against disease due to 6A and 19A is not clear. The rationale for inclusion of 6A and 19A components in a 13vPnC vaccine is discussed below.

b. Responses to 6A and 19A Induced by 6B and 19F Polysaccharides

The licensed unconjugated pneumococcal polysaccharide vaccines (for use in persons at least two years of age) have contained 6A or 6B capsular polysaccharide but not both [21]. Immunogenicity data generated at the time of formulation of the 23-valent pneumococcal polysaccharide vaccine demonstrated that a 6B monovalent vaccine induced antibody to both the 6A and 6B capsules. The data from several trials assessing IgG and opsonophagocytic assay (OPA) responses in a variety of populations with free polysaccharide and with pneumococcal conjugate vaccines suggested that IgG responses to 6A are induced by 6B antigens, but the responses are generally lower, and the OPA activity with 6A organisms is different than with 6B organisms [22, 23, 24, 25]. In addition, subjects responding with high 6B antibody may have little or no activity against 6A.

In contrast to the chemical composition of the 6A and 6B capsular polysaccharides where there exists a high degree of similarity, the 19A and 19F capsules are quite different due to the presence of two additional side chains in the 19A polysaccharide. Not surprisingly, immune responses measured in human volunteers immunized with 19F polysaccharide vaccine showed that responses to 19F were induced in 80% of subjects, but only 20% of subjects had a response to 19A [26]. Low levels of cross-reactive IgG and OPA responses to serotype 19A after immunization with 19F polysaccharide have also been documented in trials with conjugate vaccines as well [24, 26].

Internal data on cross-reactive OPA responses to 6A and 19A have been generated from the 7vPnC bridging trial (D118-P16) conducted in US infants (FIG. 3). These studies are consistent with the findings of others, and demonstrate induction of cross-reactive functional antibody to 6A polysaccharide after immunization with 6B polysaccharide, although at a lower level, and very little functional antibody to 19A after immunization with 19F.

Impact of 6B and 19F Immunization on 6A and 19A in Animal Models

Animal models have been used to evaluate the potential for cross-protection with polysaccharide immunization. In an otitis media model developed by Giebink et al., chinchillas were immunized with a tetravalent polysaccharide outer membrane protein (OMP) conjugate vaccine (containing 6B, 14, 19F, 23F saccharides) or placebo [27]. In this trial there appeared to be some cross-protection for 6A; however this did not reach statistical significance and the level of protection was lower than with 6B against otitis media. In this same model there was 100% protection against 19F otitis media, but only 17% protection against 19A otitis media.

Saeland et al. used sera from infants immunized with an 8-valent pneumococcal tetanus conjugate vaccine (containing 6B and 19F) to passively immunize mice prior to an intranasal challenge with 6A organisms, in a lung infection model [28]. Of the 59 serum samples, 53% protected mice against bacteremia with 6B and 37% protected against 6A. Mice passively immunized with sera from infants immunized with four doses of an 11-valent pneumococcal conjugate vaccine (containing 19F conjugated to tetanus toxoid) were given an intranasal challenge with 19A organisms in the same model [29]. Of 100 mice passively immunized and then challenged, 60 mice had no 19A organisms detected in lung tissue, whereas organisms were identified in all mice given saline placebo. However, passive immunization did not protect against challenge with 19F organisms in this model; therefore, the relevance of the model for serogroup 19 is questionable. In general these models provide evidence of some biological impact of 6B immunization on 6A organisms although the effect on the heterologous serotype was not as great as that observed with the homologous serotype. The impact of 19F immunization on 19A organisms is not well understood from these models.

Impact of 6B and 19F Polysaccharide Conjugate Immunization on 6A and 19A Disease in Efficacy/Effectiveness Trials

The number of cases of disease due to the 6B, 6A, 19F and 19A serotypes in 7vPnC and 9vPnC (7vPnC plus serotypes 1 and 5) efficacy trials is noted in Table 1 [30, 10, 31]. The numbers of invasive disease cases are too small to allow any conclusions to be drawn for serotypes 6A and 19A. However, the Finnish otitis media trial generated a large number of pneumococcal isolates [32]. In the per protocol analysis 7vPnC was 84% (95% CI 62%, 93%) efficacious against otitis media due to serotype 6B and 57% (95% CI 24%, 76%) efficacious against otitis media due to serotype 6A (Table 1). In contrast, serotype-specific efficacy with the 7vPnC was not demonstrated for otitis media due to either 19F or 19A. TABLE 1 Cases of Pneumococcal Disease Due to Serotypes 6B, 6A, 19F, and 19A in Efficacy Trials with the 7vPnC and 9vPnC Vaccines 6B 6A 19F 19A PnC Contr. PnC Contr. PnC Contr. PnC Contr. Kaiser Efficacy Trial - 7vPnC 1 7 0 1  2* 13 0 1 (ITT) Navajo Efficacy Trial - 7vPnC 0 5 1 0 1 1 1 0 (ITT) South African Efficacy Trial - 1 2 1 0 0 1 3 1 9vPnC HIV (−) (ITT) South African Efficacy Trial - 1 7 3 10 2 3 2 3 9vPnC HIV (+) (ITT) Finnish Otitis Media Trial -  9* 56 19* 45 43  58 17 26 7vPnC (PP) *Statistically significant efficacy demonstrated From references 30, 10 and 33, and personal communications Contr = control ITT = intention to treat analysis PP = per protocol analysis

Post-marketing IPD surveillance data is also available from a case-control trial conducted by the Centers for Disease Control to evaluate the effectiveness of Prevnar [33]. Cases of pneumococcal invasive disease occurring in children 3 to 23 months of age were identified in the surveillance laboratories and matched with three control cases by age and zip code. After obtaining consent, medical and immunization history (subjects were considered immunized if they had received at least one dose of Prevnar) was obtained from parents and medical providers for cases and controls. The preliminary results were presented at the 2003 ICAAC meeting and a summary of the findings for 6B, 19F, 19A and 6A disease is presented in Table 2. These data indicate that Prevnar is able to prevent disease due to 6A, although at a level that may be somewhat lower than serotype 6B disease. These data also indicate that the cross-protection for invasive disease due to 19A is limited. TABLE 2 Preliminary results of a Case Control Trial Performed by the CDC (presented at ICAAC, 2003) VE* Serotype Informative Sets, n (95% CI) Vaccine Type, All 115 94 (87, 97) Vaccine Related, All 36 70 (38, 86) Non-Vaccine Type, All 43 −4 (−106, 48)    6B 27 94 (72, 99) 19F 19 73 (16, 92) 6A 15 87 (53, 97) 19A 16 40 (−87, 80)   *Vaccine effectiveness comparing vaccinated (≧1 dose) vs. unvaccinated, and adjusted for underlying conditions Reference 40 and personal/confidential communication

A published analysis [3] of the use of Prevnar also indicated that serotypes 6B and 19F conferred a moderate reduction in IPD caused by serotypes 6A and 19A among children under two years of age (Table 1 in [3]). Disease rates among unimmunized adults caused by serotypes 6A, 9A, 9L, 9N, 18A, 18B, 18F, 19A, 19B, 19C, 23A and 23B (“all vaccine-related serotypes”) were somewhat reduced (Table 2 in [3]). These data establish that herd immunity from the use of Prevnar in children under two years of age was modest for serotypes 6A and 19A, and provide a basis for the inclusion of serotypes 6A and 19A in the 13vPnC vaccine of this invention.

Conclusion for Addition of 6A and 19A

The post-marketing surveillance data and the case-control study results noted in FIG. 1 and Table 2 with the 7vPnC vaccine suggest that, consistent with the other information on immune responses and performance in the animals models described above, there may be some cross-protection against 6A disease, but to a lesser extent than to 6B disease. Furthermore, it appears the protection against 19A is limited. Therefore, a 13vPnC vaccine containing serotypes 6A and 19A provides coverage that is not dependent on the limitations of serogroup cross-protection by serotypes 6B and 19F.

Accordingly, the present invention provides a multivalent immunogenic composition comprising 13 distinct polysaccharide-protein conjugates, wherein each of the conjugates contains a different capsular polysaccharide conjugated to a carrier protein, and wherein the capsular polysaccharides are prepared from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F of Streptococcus pneumoniae, together with a physiologically acceptable vehicle. One such carrier protein is the diphtheria toxoid designated CRM₁₉₇. The immunogenic composition may further comprise an adjuvant, such as an aluminum-based adjuvant, such as aluminum phosphate, aluminum sulfate and aluminum hydroxide.

Capsular polysaccharides are prepared by standard techniques known to those skilled in the art. In the present invention, capsular polysaccharides are prepared from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F of Streptococcus pneumoniae. These pneumococcal conjugates are prepared by separate processes and formulated into a single dosage formulation. For example, in one embodiment, each pneumococcal polysaccharide serotype is grown in a soy-based medium. The individual polysaccharides are then purified through centrifugation, precipitation, ultra-filtration, and column chromatography. The purified polysaccharides are chemically activated to make the saccharides capable of reacting with the carrier protein.

Once activated, each capsular polysaccharide is separately conjugated to a carrier protein to form a glycoconjugate. In one embodiment, each capsular polysaccharide is conjugated to the same carrier protein. In this embodiment, the conjugation is effected by reductive amination.

The chemical activation of the polysaccharides and subsequent conjugation to the carrier protein are achieved by conventional means. See, for example, U.S. Pat. Nos. 4,673,574 and 4,902,506 [34, 35].

Carrier proteins are preferably proteins /that are non-toxic and non-reactogenic and obtainable in sufficient amount and purity. Carrier proteins should be amenable to standard conjugation procedures. In a particular embodiment of the present invention, CRM₁₉₇ is used as the carrier protein.

CRM₁₉₇ (Wyeth, Sanford, N.C.) is a non-toxic variant (i.e., toxoid) of diphtheria toxin isolated from cultures of Corynebacterium diphtheria strain C7 (β197) grown in casamino acids and yeast extract-based medium. CRM₁₉₇ is purified through ultra-filtration, ammonium sulfate precipitation, and ion-exchange chromatography. Alternatively, CRM₁₉₇ is prepared recombinantly in accordance with U.S. Pat. No. 5,614,382, which is hereby incorporated by reference. Other diphtheria toxoids are also suitable for use as carrier proteins.

Other suitable carrier proteins include inactivated bacterial toxins such as tetanus toxoid, pertussis toxoid, cholera toxoid (e.g., as described in International Patent Application WO2004/083251 [38]), E. coli LT, E. coli ST, and exotoxin A from Pseudomonas aeruginosa. Bacterial outer membrane proteins such as outer membrane complex c (OMPC), porins, transferrin binding proteins, pneumolysin, pneumococcal surface protein A (PspA), pneumococcal adhesin protein (PsaA), C5a peptidase from Group A or Group B streptococcus, or Haemophilus influenzae protein D, can also be used. Other proteins, such as ovalbumin, keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA) or purified protein derivative of tuberculin (PPD) can also be used as carrier proteins.

After conjugation of the capsular polysaccharide to the carrier protein, the polysaccharide-protein conjugates are purified (enriched with respect to the amount of polysaccharide-protein conjugate) by a variety of techniques. These techniques include concentration/diafiltration operations, precipitation/elution, column chromatography, and depth filtration. See examples below.

After the individual glycoconjugates are purified, they are compounded to formulate the immunogenic composition of the present invention, which can be used as a vaccine. Formulation of the immunogenic composition of the present invention can be accomplished using art-recognized methods. For instance, the 13 individual pneumococcal conjugates can be formulated with a physiologically acceptable vehicle to prepare the composition. Examples of such vehicles include, but are not limited to, water, buffered saline, polyols (e.g., glycerol, propylene glycol, liquid polyethylene glycol) and dextrose solutions.

In certain embodiments, the immunogenic composition will comprise one or more adjuvants. As defined herein, an “adjuvant” is a substance that serves to enhance the immunogenicity of an immunogenic composition of this invention. Thus, adjuvants are often given to boost the immune response and are well known to the skilled artisan. Suitable adjuvants to enhance effectiveness of the composition include, but are not limited to:

(1) aluminum salts (alum), such as aluminum hydroxide, aluminum phosphate, aluminum sulfate, etc.;

(2) oil-in-water emulsion formulations (with or without other specific immunostimulating agents such as muramyl peptides (defined below) or bacterial cell wall components), such as, for example,

-   -   (a) MF59 (PCT Publ. No. WO 90/14837), containing 5% Squalene,         0.5% Tween 80, and 0.5% Span 85 (optionally containing various         amounts of MTP-PE (see below, although not required)) formulated         into submicron particles using a microfluidizer such as Model         110Y microfluidizer (Microfluidics, Newton, Mass.),     -   (b) SAF, containing 10% Squalene, 0.4% Tween 80, 5%         pluronic-blocked polymer L121, and thr-MDP (see below) either         microfluidized into a submicron emulsion or vortexed to generate         a larger particle size emulsion, and     -   (c) Ribi™ adjuvant system (RAS), (Corixa, Hamilton, Mont.)         containing 2% Squalene, 0.2% Tween 80, and one or more bacterial         cell wall components from the group consisting of 3-O-deaylated         monophosphorylipid A (MPL™) described in U.S. Pat. No. 4,912,094         (Corixa), trehalose dimycolate (TDM), and cell wall skeleton         (CWS), preferably MPL+CWS (Detox™);

(3) saponin adjuvants, such as Quil A or STIMULON™ QS-21 (Antigenics, Framingham, Mass.) (U.S. Pat. No. 5,057,540) may be used or particles generated therefrom such as ISCOMs (immunostimulating complexes);

(4) bacterial lipopolysaccharides, synthetic lipid A analogs such as aminoalkyl glucosamine phosphate compounds (AGP), or derivatives or analogs thereof, which are available from Corixa, and which are described in U.S. Pat. No. 6,113,918; one such AGP is 2-[(R)-3-Tetradecanoyloxytetradecanoylamino]ethyl 2-Deoxy-4-O-phosphono-3-O—[(R)-3-tetradecanoyloxytetradecanoyl]-2-[(R)-3-tetradecanoyloxytetradecanoylamino]-b-D-glucopyranoside, which is also know as 529 (formerly known as RC529), which is formulated as an aqueous form or as a stable emulsion, synthetic polynucleotides such as oligonucleotides containing CpG motif(s) (U.S. Pat. No. 6,207,646);

(5) cytokines, such as interleukins (e.g., IL-1, IL-2, IL-4, IL-5, IL-6, IL-7, IL-12, IL-15, IL-18, etc.), interferons (e.g., gamma interferon), granulocyte macrophage colony stimulating factor (GM-CSF), macrophage colony stimulating factor (M-CSF), tumor necrosis factor (TNF), costimulatory molecules B7-1 and B7-2, etc.;

(6) detoxified mutants of a bacterial ADP-ribosylating toxin such as a cholera toxin (CT) either in a wild-type or mutant form, for example, where the glutamic acid at amino acid position 29 is replaced by another amino acid, preferably a histidine, in accordance with published international patent application number WO 00/18434 (see also WO 02/098368 and WO 02/098369), a pertussis toxin (PT), or an E. coli heat-labile toxin (LT), particularly LT-K63, LT-R72, CT-S109, PT-K9/G129 (see, e.g., WO 93/13302 and WO 92/19265); and

(7) other substances that act as immunostimulating agents to enhance the effectiveness of the composition.

Muramyl peptides include, but are not limited to, N-acetyl-muramyl-L-threonyl-D-isoglutamine (thr-MDP), N-acetyl-normuramyl-L-alanine-2-(1′-2′ dipalmitoyl-sn-glycero-3-hydroxyphosphoryloxy)-ethylamine (MTP-PE), etc.

The vaccine formulations of the present invention can be used to protect or treat a human susceptible to pneumococcal infection, by means of administering the vaccine via a systemic or mucosal route. These administrations can include injection via the intramuscular, intraperitoneal, intradermal or subcutaneous routes; or via mucosal administration to the oral/alimentary, respiratory or genitourinary tracts. In one embodiment, intranasal administration is used for the treatment of pneumonia or otitis media (as nasopharyngeal carriage of pneumococci can be more effectively prevented, thus attenuating infection at its earliest stage).

The amount of conjugate in each vaccine dose is selected as an amount that induces an immunoprotective response without significant, adverse effects. Such amount can vary depending upon the pneumococcal serotype. Generally, each dose will comprise 0.1 to 100 μg of polysaccharide, particularly 0.1 to 10 μg, and more particularly 1 to 5 μg.

Optimal amounts of components for a particular vaccine can be ascertained by standard studies involving observation of appropriate immune responses in subjects. Following an initial vaccination, subjects can receive one or several booster immunizations adequately spaced.

In a particular embodiment of the present invention, the 13vPnC vaccine is a sterile liquid formulation of pneumococcal capsular polysaccharides of serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F individually conjugated to CRM₁₉₇. Each 0.5 mL dose is formulated to contain: 2 μg of each saccharide, except for 6B at 4 μg; approximately 29 μg CRM₁₉₇ carrier protein; 0.125 mg of elemental aluminum (0.5 mg aluminum phosphate) adjuvant; and sodium chloride and sodium succinate buffer as excipients. The liquid is filled into single dose syringes without a preservative. After shaking, the vaccine is a homogeneous, white suspension ready for intramuscular administration.

The choice of dose level for the 13vPnC vaccine is similar to the marketed 7vPnC vaccine (Prevnar). The 2 μg saccharide dose level was selected for all serotypes, except for 6B, which is at 4 μg per dose. The 7vPnC vaccine has shown desirable safety, immunogenicity, and efficacy against IPD in the 2 μg saccharide dose level for serotypes 4, 9V, 14, 18C, 19F and 23F, and at the 4 μg dose for 6B.

The immunization schedule can follow that designated for the 7vPnC vaccine. For example, the routine schedule for infants and toddlers against invasive disease caused by S. pneumoniae due to the serotypes included in the 13vPnC vaccine is 2, 4, 6 and 12-15 months of age. The compositions of this invention are also suitable for use with older children, adolescents and adults.

The compositions of this invention may further include one or more additional antigens for use against otitis media caused by infection with other bacteria. Such bacteria include nontypable Haemophilus influenza, Moraxella catarrhalis (formerly known as Branhamella catarrhalis) and Alloiococcus otitidis.

Examples of nontypable Haemophilus influenzae antigens suitable for inclusion include the P4 protein, also known as protein “e” (U.S. Pat. No. 5,601,831; International Patent Application WO03/078453), the P6 protein, also known as the PAL or the PBOMP-1 protein (U.S. Pat. No. 5,110,908; International Patent Application WO0100790), the P5 protein (U.S. Reissue Pat. No. 37,741), the Haemophilus adhesion and penetration protein (U.S. Pat. Nos. 6,245,337 and 6,676,948), the LKP tip adhesin protein (U.S. Pat. No. 5,643,725) and the NucA protein (U.S. Pat. No. 6,221,365).

Examples of Moraxella catarrhalis antigens suitable for inclusion include the UspA2 protein (U.S. Pat. Nos. 5,552,146, 6,310,190), the CD protein (U.S. Pat. No. 5,725,862), the E protein (U.S. Pat. No. 5,948,412) and the 74 kilodalton outer membrane protein (U.S. Pat. No. 6,899,885).

Examples of Alloiococcus otitidis antigens suitable for inclusion include those identified in International Patent Application WO03/048304.

The compositions of this invention may also include one or more proteins from Streptococcus pneumoniae. Examples of Streptococcus pneumoniae proteins suitable for inclusion include those identified in International Patent Application WO02/083855, as well as that described in International Patent Application WO02/053761.

The compositions of this invention may further include one or more proteins from Neisseria meningitidis type B. Examples of Neisseria meningitidis type B proteins suitable for inclusion include those identified in International Patent Applications WO03/063766, WO2004/094596, WO01/85772, WO02/16612 and WO01/87939.

Activation of S. pneumoniae Serotype 3 Polysaccharide for Conjugation

Partial oxidation of carbohydrates in polysaccharides has been effectively utilized to generate aldehyde groups which are then coupled to the lysine residues of carrier proteins to generate immunogenic conjugates (i.e., compositions, such as vaccines, useful for stimulating or eliciting a specific immune response in a vertebrate). For many applications, the general purpose oxidizing agent sodium periodate provides effective oxidation of carbohydrates in polysaccharides prior to conjugation with carrier proteins. However, direct oxidation of Pn 3 polysaccharide with sodium periodate can result in degraded polysaccharide with few remaining aldehydes present. An alternate oxidation procedure incorporates periodic acid in the presence of bivalent cations (e.g., Mg²⁺ or Ca²⁺) and provides effective oxidation of Pn 3 polysaccharide (Table 3). TABLE 3 Oxidation Data of Pn 3 using Periodic Acid/MgCl₂ Periodic Acid amount Oxidation Kd # Sample ID (meq)** (hours) Temp (° C.) DO#*** (CL4B) PP3* Native 0 — 4 0.0 0.048 PP3 Oxidized 0.2 16 25 5.8 0.24 PP3 Oxidized 0.2 72 4 9.0 0.1 PP3 Oxidized 1 16 4 13.2 0.24 PP3 Oxidized 1 16 25 4.1 0.24 PP3 Oxidized 1 72 4 7.9 0.29 *PP3: native Pneumo Polysaccharide type 3 **Meq: mole equivalent ***DO: degree of oxidation

In order to reduce viscosity and associated filtration issues, the Pn 3 polysaccharide is first subjected to hydrolysis/depolymerization using a mild acid, such as acetic acid, citric acid or carbonic acid. Partial oxidation to produce “activated” Pn 3 polysaccharide is carried out following hydrolysis/depolymerization using controlled amounts of an oxidizing agent. Any selective oxidizing agent which oxidizes a terminal hydroxyl group to an aldehyde, including specific sugar oxidases, can be used (e.g., sodium or potassium periodate, or periodic acid). As discussed above, a preferred oxidizing agent is periodic acid in the presence of bivalent cations. The activated Pn 3 polysaccharide is then optionally purified (e.g., by diafiltration versus buffered saline).

Activated Pn 3 polysaccharide can be compounded with a carrier protein. Carrier proteins are chosen to increase the immunogenicity of the bound Pn 3 polysaccharide and/or to elicit antibodies against the carrier protein which are diagnostically, analytically and/or therapeutically beneficial. Covalent linking of an antigenic molecule (e.g., a polysaccharide) to a carrier confers enhanced immunogenicity and T-cell dependence (Pozsgay et al. (1999) PNAS, 96:5194-97; Lee et al. (1976) J. Immunol., 116:1711-18; Dintzis et al. (1976) PNAS, 73:3671-75). As described herein, useful carrier proteins include inactivated bacterial toxins such as tetanus toxoid, pertussis toxoid, cholera toxoid (e.g., as described in International Patent Application WO2004/083251), E. coli LT, E. coli ST, and exotoxin A from Pseudomonas aeruginosa. Bacterial outer membrane proteins such as outer membrane complex c, porins, transferrin binding proteins, pneumolysin, pneumococcal surface protein A, pneumococcal adhesin protein, C5a peptidase from Group A or Group B streptococcus, or Haemophilus influenzae protein D, can also be used. Other proteins, such as ovalbumin, keyhole limpet hemocyanin, bovine serum albumin, or purified protein derivative of tuberculin can also be used as carrier proteins. A preferred carrier protein is the mutated diphtheria toxin CRM₁₉₇. Following compounding with the carrier protein, the activated Pn 3 polysaccharide/carrier protein mixture is optionally frozen (e.g., shell frozen) and co-lyophilized.

Conjugation is carried out by reacting the activated Pn 3 polysaccharide/carrier protein mixture with a reducing agent, such as sodium cyanoborohydride. Unreacted aldehydes are then capped via sodium borohydride reduction. The conjugate is purified (e.g., by diafiltration versus phosphate buffer followed by buffered saline), giving a final batch concentrate of the glycoconjugate in buffered saline.

The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific examples. These examples are described solely for the purpose of illustration and are not intended to limit the scope of the invention.

EXAMPLES Example 1 Preparation of S. Pneumoniae Capsular Polysaccharide Serotype 1 Preparation of Master and Working Cell Banks

S. pneumoniae serotype 1 was obtained from the American Type Culture Collection, ATCC, strain 6301. Several generations of seed stocks were created in order to expand the strain and remove components of animal origin (generations F1, F2, and F3). Two additional generations of seed stocks were produced. The first additional generation was made from an F3 vial, and the subsequent generation was made from a vial of the first additional generation. Seed vials were stored frozen (<−70° C.) with synthetic glycerol as a cryopreservative. In addition to frozen vials, lyophilized vials were prepared for the F4 generation. For cell bank preparation, all cultures were grown in a soy-based medium. Prior to freezing, cells were concentrated by centrifugation, spent medium was removed, and cell pellets were re-suspended in fresh medium containing a cryopreservative, such as synthetic glycerol.

Fermentation and Harvesting

Cultures from the working cell bank were used to inoculate seed bottles containing a soy-based medium. The bottles were incubated at 36° C.±2° C. without agitation until growth requirements were met. A seed bottle was used to inoculate a seed fermentor containing soy-based medium. A pH of about 7.0 was maintained with sterile sodium carbonate solution. After the target optical density was reached, the seed fermentor was used to inoculate the production fermentor containing soy-based medium. The pH was maintained with sterile sodium carbonate solution. The fermentation was terminated after cessation of growth or when the working volume of the fermentor was reached. An appropriate amount of sterile 12% deoxycholate sodium was added to the culture to lyse the bacterial cells and release cell-associated polysaccharide. After lysing, the fermentor contents were cooled. The pH of the lysed culture broth was adjusted to approximately pH 6.6 with acetic acid. The lysate was clarified by continuous flow centrifugation followed by depth filtration and 0.45 μm microfiltration.

In an alternate process, the fermentation pH of about 7.0 was maintained with 3N NaOH. After the target optical density was reached, the seed fermentor was used to inoculate the production fermentor containing soy-based medium. The pH was maintained with 3N NaOH. The fermentation was terminated after cessation of growth or when the working volume of the fermentor was reached. An appropriate amount of sterile 12% deoxycholate sodium was added to the culture to obtain a 0.12% concentration in the broth, to lyse the bacterial cells and release cell-associated polysaccharide. After lysing, the fermentor contents were held, with agitation, for a time interval between 8 and 24 hours at a temperature between 7° C. and 13° C., to assure that complete cellular lysis and polysaccharide release had occurred. Agitation during this hold period prevented lysate sediment from settling on the fermentor walls and pH probe, thereby allowing the pH probe integrity to be maintained. Next, the pH of the lysed culture broth was adjusted to approximately pH 5.0 with 50% acetic acid. After a hold time without agitation, for a time interval between 12 and 24 hours at a temperature between 15° C. and 25° C., a significant portion of the previously soluble proteins dropped out of solution as a solid precipitate with little loss or degradation of the polysaccharide, which remained in solution. The solution with the precipitate was then clarified by continuous flow centrifugation followed by depth filtration and 0.45 μm microfiltration.

Purification

The purification of the pneumococcal polysaccharide consisted of several concentration/diafiltration operations, precipitation/elution, column chromatography, and depth filtration steps. All procedures were performed at room temperature unless otherwise specified.

Clarified broth from the fermentor cultures of S. pneumoniae serotype 1 were concentrated and diafiltered using a 100 kDa MWCO (kilodalton molecular weight cutoff) filter. Diafiltration was accomplished using sodium phosphate buffer at neutral pH. Diafiltration removed the low molecular weight medium components from the higher molecular weight biopolymers such as nucleic acid, protein and polysaccharide.

The polysaccharide was precipitated from the concentrated and diafiltered solution by adding hexadecyltrimethyl ammonium bromide (HB) from a stock solution to give a final concentration of 1% HB (w/v). The polysaccharide/HB precipitate was captured on a depth filter and the filtrate was discarded. The polysaccharide precipitate was resolubilized and eluted by recirculating a sodium chloride solution through the precipitate-containing depth filter. The filters were then rinsed with additional sodium chloride solution.

Sodium iodide (NaI) was added to the polysaccharide solution from a stock NaI solution to achieve a final concentration of 0.5% to precipitate HB. The precipitate was removed by depth filtration. The filtrate contains the target polysaccharide. The precipitation vessel and the filter were rinsed with a NaCl/NaI solution and the rinse was combined with the partially purified polysaccharide solution. The filter was discarded. The polysaccharide was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and diafiltered with a sodium chloride solution.

The partially purified polysaccharide solution was further purified by filtration through a depth filter impregnated with activated carbon. After filtration, the carbon filter was rinsed with a sodium chloride solution. The rinse is combined with the polysaccharide solution, which is then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and adjusted with a 1M sodium phosphate buffer to achieve a final concentration of 0.025 M sodium phosphate. The pH was checked and adjusted to 7.0±0.2.

The ceramic hydroxyapatite (HA) column was equilibrated with sodium phosphate buffer containing sodium chloride to obtain the appropriate conductivity (<15 μS). The polysaccharide solution was then loaded onto the column. Under these conditions, impurities bound to the resin and the polysaccharide was recovered in the flow-through from the column. The polysaccharide solution was filtered through 0.2 μm inline filters located before and after the column.

The polysaccharide solution was concentrated using a 30 kDa MWCO filter. The concentrate was then diafiltered with Water for Injection (WFI).

The diafiltered polysaccharide solution was filtered through a 0.2 μm membrane filter into polypropylene bottles. Samples were removed for release testing and the purified polysaccharide was stored frozen at −25°±5° C.

Characterization

The 1H-NMR data was consistent with the chemical structure by the assignment of signals assigned to the protons of the polysaccharide molecule. The 1H-NMR spectrum showed a series of well-resolved signals (protons from the methyl group) for the quantitation of the O-acetyl functional group in the polysaccharide.

The identity of the monovalent polysaccharide was confirmed by countercurrent immunoelectrophoresis using specific antisera.

High performance gel filtration chromatography coupled with refractive index and multiangle laser light scattering (MALLS) detectors was used in conjunction with the sample concentration to calculate the molecular weight.

Size exclusion chromatography media (CL-4B) was used to profile the relative molecular size distribution of the polysaccharide.

Example 2 Preparation of Serotype 1 Pneumococcal Saccharide—CRM₁₉₇ Conjugate Activation and Conjugation

Containers of purified polysaccharide were thawed and combined in a reaction vessel. To the vessel, 0.2 M sodium carbonate, pH 9.0 was added for partial deacetylation (hydrolysis) for 3 hours at 50° C. The reaction was cooled to 20° C. and neutralization was performed by 0.2 M acetic acid. Oxidation in the presence of sodium periodate was performed by incubation at 2-8° C., and the mixture was stirred for 15-21 hours.

The activation reaction mixture was concentrated and diafiltered 10× with 0.9% NaCl using a 30K MWCO membrane. The retentate was 0.2 μm filtered. The activated saccharide was filled into 100 mL glass lyophilization bottles and shell-frozen at −75° C. and lyophilized.

“Shell-freezing” is a method for preparing samples for lyophilization (freeze-drying). Flasks are automatically rotated by motor driven rollers in a refrigerated bath containing alcohol or any other appropriate fluid. A thin coating of product is evenly frozen around the inside “shell” of a flask, permitting a greater volume of material to be safely processed during each freeze-drying run. These automatic, refrigerated units provide a simple and efficient means of pre-freezing many flasks at a time, producing the desired coatings inside, and providing sufficient surface area for efficient freeze-drying.

Bottles of lyophilized material were brought to room temperature and resuspended in CRM₁₉₇ solution at a saccharide/protein ratio of 2:1. To the saccharide/protein mixture 1M sodium phosphate buffer was added to a final 0.2M ionic strength and a pH of 7.5, then sodium cyanoborohydride was added. The reaction was incubated at 23° C. for 18 hours, followed by a second incubation at 37° C. for 72 hours. Following the cyanoborohydride incubations, the reaction mixture was diluted with cold saline followed by the addition of 1M sodium carbonate to adjust the reaction mixture to pH 9.0. Unreacted aldehydes were quenched by addition of sodium borohydride by incubation at 23° C. for 3-6 hours.

The reaction mixture was diluted 2-fold with saline and transferred through a 0.45-5 μm prefilter into a retentate vessel. The reaction mixture is diafiltered 30× with 0.15 M phosphate buffer, pH 6, and 20× with saline. The retentate was filtered through a 0.2 μm filter.

The conjugate solution was diluted to a target of 0.5 mg/mL in 0.9% saline, and then sterile filtered into final bulk concentrate (FBC) containers in a Class 100 hood. The conjugate was stored at 2-8° C.

Characterization

Size exclusion chromatography media (CL-4B) was used to profile the relative molecular size distribution of the conjugate.

The identity of the conjugate was confirmed by the slot-blot assay using specific antisera.

The saccharide and protein concentrations were determined by the uronic acid and Lowry assays, respectively. The ratio of saccharide to protein in the covalently bonded conjugate complex was obtained by the calculation: ${Ratio} = \frac{{{µg}/{mL}}\quad{saccharide}}{{{µg}/{mL}}\quad{protein}}$

O-acetyl content was measured by the Hestrin method (Hestrin et. al., J. Biol. Chem. 1949, 180, p. 249). The ratio of O-acetyl concentration to total saccharide concentration gave μmoles of O-acetyl per mg of saccharide.

Example 3 Preparation of S. Pneumoniae Capsular Polysaccharide Serotype 3 Preparation of Master and Working Cell Banks

S. pneumoniae serotype 3 was obtained from Dr. Robert Austrian, University of Pennsylvania, Philadelphia, Pa. For preparation of the cell bank system, see Example 1.

Fermentation and Harvesting

Cultures from the working cell bank were used to inoculate seed bottles containing soy-based medium. The bottles were incubated at 36° C.±2° C. without agitation until growth requirements were met. A seed bottle was used to inoculate a seed fermentor containing soy-based medium. A pH of about 7.0 was maintained with sterile sodium carbonate solution. After the target optical density was reached, the seed fermentor was used to inoculate an intermediate seed fermentor. After the target optical density was reached, the intermediate seed fermentor was used to inoculate the production fermentor. The pH was maintained with sterile sodium carbonate solution. The fermentation was terminated after the working volume of the fermentor was reached. An appropriate amount of sterile 12% sodium deoxycholate was added to the culture to lyse the bacterial cells and release cell-associated polysaccharide. After lysing, the fermentor contents were cooled. The pH of the lysed culture broth was adjusted to approximately pH 6.6 with acetic acid. The lysate was clarified by continuous flow centrifugation followed by depth filtration and 0.45 μm microfiltration.

Purification

The purification of the pneumococcal polysaccharide consisted of several concentration/diafiltration operations, precipitation/elution, column chromatography, and depth filtration steps. All procedures were performed at room temperature unless otherwise specified.

Clarified broth from the fermentor cultures of S. pneumoniae serotype 3 were concentrated and diafiltered using a 100 kDa MWCO filter. Diafiltration was accomplished using sodium phosphate buffer at neutral pH. Diafiltration removed the low molecular weight medium components from the higher molecular weight biopolymers such as nucleic acid, protein and polysaccharide.

Prior to the addition of hexadecyltrimethyl ammonium bromide (HB), a calculated volume of a NaCl stock solution was added to the concentrated and diafiltered polysaccharide solution to give a final concentration of 0.25 M NaCl. The polysaccharide was then precipitated by adding HB from a stock solution to give a final concentration of 1% HB (w/v). The polysaccharide/HB precipitate was captured on a depth filter and the filtrate was discarded. The polysaccharide precipitate was resolubilized and eluted by recirculating a sodium chloride solution through the precipitate-containing depth filter. The filters were then rinsed with additional sodium chloride solution.

Sodium iodide (NaI) was added to the polysaccharide solution from a stock NaI solution to achieve a final concentration of 0.5% to precipitate HB. The precipitate was removed by depth filtration. The filtrate contained the target polysaccharide. The precipitation vessel and the filter were rinsed with a NaCl/NaI solution and the rinse was combined with the partially purified polysaccharide solution. The filter was discarded. The polysaccharide was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and diafiltered with a sodium chloride solution.

The partially purified polysaccharide solution was further purified by filtration through a depth filter impregnated with activated carbon. After filtration, the carbon filter was rinsed with a sodium chloride solution. The rinse was combined with the polysaccharide solution, which was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and adjusted with a 1M sodium phosphate buffer to achieve a final concentration of 0.025M sodium phosphate. The pH was checked and adjusted to 7.0±0.2.

The ceramic hydroxyapatite (HA) column was equilibrated with sodium phosphate buffer containing sodium chloride to obtain the appropriate conductivity (15 μS). The polysaccharide solution was then loaded onto the column. Under these conditions, impurities bound to the resin and the polysaccharide was recovered in the flow-through from the column. The polysaccharide was flushed through the column with buffer and was filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated using a 30 kDa MWCO filter. The concentrate was then diafiltered with WFI.

The diafiltered polysaccharide solution was filtered through a 0.2 μm membrane filter into stainless steel containers. Samples were removed for release testing and the purified polysaccharide was stored frozen at −25°±5° C.

Characterization

The 1H-NMR data was consistent with the chemical structure by the assignment of signals assigned to the protons of the polysaccharide molecule.

The identity of the monovalent polysaccharide was confirmed by countercurrent immunoelectrophoresis using specific antisera.

High performance gel filtration chromatography, coupled with refractive index and multiangle laser light scattering (MALLS) detectors, was used in conjunction with the sample concentration to calculate the molecular weight.

Size exclusion chromatography media (CL-4B) was used to profile the relative molecular size distribution of the polysaccharide.

Example 4 Preparation of Serotype 3 Pneumococcal Saccharide—CRM₁₉₇ Conjugate Activation and Conjugation

Containers of purified serotype 3 saccharide were thawed and combined in a reaction vessel. To the vessel, WFI and 2M acetic acid were added to a final concentration of 0.2M and 2 mg/mL saccharide. The temperature of the solution was raised to 85° C. for one hour to hydrolyze the polysaccharide. The reaction was cooled to ≦25° C. and 1M magnesium chloride was added to a final concentration of 0.1M. Oxidation in the presence of sodium periodate was performed by incubation for 16-24 hours at 23° C.

The activation reaction mixture was concentrated and diafiltered 10× with WFI using a 100K MWCO membrane. The retentate was filtered through a 0.2-μm filter.

For compounding, 0.2M sodium phosphate, pH 7.0, was added to the activated saccharide to a final concentration of 10 mM and a pH of 6.0-6.5. CRM₁₉₇ carrier protein was mixed with the saccharide solution to a ratio of 2 g of saccharide per 1 g of CRM₁₉₇. The combined saccharide/protein solution was filled into 100 mL glass lyophilization bottles with a 50 mL target fill, shell-frozen at −75° C., and lyophilized.

Bottles of co-lyophilized saccharide/protein material were brought to room temperature and resuspended in 0.1M sodium phosphate buffer, pH 7.0, to a final saccharide concentration of 20 mg/mL. The pH was adjusted to 6.5 and then a 0.5 molar equivalent of sodium cyanoborohydride was added. The reaction was incubated at 37° C. for 48 hours. Following the cyanoborohydride incubation, the reaction mixture was diluted with cold 5 mM succinate/0.9% saline buffer. Unreacted aldehydes were quenched by the addition of sodium borohydride and incubation at 23° C. for 3-6 hours. The reaction mixture was transferred through a 0.45-5 μm prefilter into a retentate vessel.

The reaction mixture was diafiltered 30× with 0.1M phosphate buffer (pH 9), 20× with 0.15M phosphate butter (pH 6), and 20× with 5 mM succinate/0.9% saline. The retentate was filtered through a 0.2-μm filter.

The conjugate solution was diluted to a saccharide target of 0.5 mg/mL, and then sterile filtered into FBC containers in a Class 100 hood. The conjugate was stored at 2-8° C.

Characterization

Size exclusion chromatography media (CL-4B) was used to profile the relative molecular size distribution of the conjugate.

The identity of the conjugate was confirmed by the slot-blot assay using specific antisera.

The saccharide and protein concentrations were determined by the Anthrone and Lowry assays, respectively. The ratio of saccharide to protein in the covalently bonded conjugate complex was obtained by the calculation: ${Ratio} = \frac{{{µg}/{mL}}\quad{saccharide}}{{{µg}/{mL}}\quad{protein}}$

Example 5 Preparation of S. Pneumoniae Capsular Polysaccharide Serotype 5

S. pneumoniae serotype 5 was obtained from Dr. Gerald Schiffman of the State University of New York, Brooklyn, N.Y. For preparation of the cell bank system, see Example 1. For fermentation, harvesting, purification and characterization of the polysaccharide, see Example 1.

Alternate Fermentation Process

Cultures from the working cell bank were used to inoculate seed bottles containing a soy-based medium and a 10 mM sterile NaHCO₃ solution. The bottles were incubated at 36° C.±2° C. without agitation until growth requirements were met. A seed bottle was used to inoculate a seed fermentor containing soy-based medium and a 10 mM sterile NaHCO₃ solution. A pH of about 7.0 was maintained with 3N NaOH. After the target optical density was reached, the seed fermentor was used to inoculate the production fermentor containing soy-based medium with a 10 mM NaHCO₃ concentration. The pH was maintained with 3N NaOH. The fermentation was terminated after cessation of growth or when the working volume of the fermentor was reached. An appropriate amount of sterile 12% sodium deoxycholate was added to the culture to obtain a 0.12% concentration in the broth, to lyse the bacterial cells and release cell-associated polysaccharide. After lysing, the fermentor contents were held, with agitation, for a time interval between 8 and 24 hours at a temperature between 7° C. and 13° C. to assure that complete cellular lysis and polysaccharide release had occurred. Agitation during this hold period prevented lysate sediment from settling on the fermentor walls and pH probe, thereby allowing the pH probe integrity to be maintained. Next, the pH of the lysed culture broth was adjusted to approximately pH 4.5 with 50% acetic acid. After a hold time without agitation, for a time interval between 12 and 24 hours at a temperature between 15° C. and 25° C., a significant portion of the previously soluble proteins dropped out of solution as a solid precipitate with little loss or degradation of the polysaccharide, which remained in solution. The solution with the precipitate was then clarified by continuous flow centrifugation followed by depth filtration and 0.45 μm microfiltration.

Example 6 Preparation of Serotype 5 Pneumococcal Saccharide—CRM₁₉₇ Conjugate Activation and Conjugation

Containers of serotype 5 saccharide were thawed and combined in a reaction vessel. To the vessel, 0.1M sodium acetate, pH 4.7, was added followed by oxidation in the presence of sodium periodate by incubation for 16-22 hours at 23° C.

The activation reaction mixture was concentrated and diafiltered 10× with WFI using a 100K MWCO membrane. The retentate was filtered through a 0.2 μm filter.

The serotype 5 activated saccharide was combined with CRM₁₉₇ at a ratio of 0.8:1. The combined saccharide/protein solution was filled into 100 mL glass lyophilization bottles (50 mL target fill), shell-frozen at −75° C., and co-lyophilized.

Bottles of co-lyophilized material were brought to room temperature and resuspended in 0.1M sodium phosphate, pH 7.5, and sodium cyanoborohydride was added. The reaction was incubated at 30° C. for 72 hours, followed by a second addition of cyanoborohydride and incubated at 30° C. for 20-28 hours.

Following the cyanoborohydride incubations, the reaction mixture was diluted 2-fold with saline and transferred through a 0.45-5 μm prefilter into a retentate vessel. The reaction mixture was diafiltered 30× with 0.01M phosphate buffer, pH 8, 20× with 0.15M phosphate buffer, pH 6, and 20× with saline. The retentate was filtered through a 0.2 μm filter.

The conjugate solution was diluted to a saccharide target of 0.5 mg/mL, and then sterile filtered into FBC containers in a Class 100 hood. The conjugate was stored at 2-8° C.

For the characterization of the conjugate, see Example 2.

Example 7 Preparation of S. Pneumoniae Capsular Polysaccharide Serotype 6A

S. pneumoniae serotype 6A was obtained from Dr. Gerald Schiffman of the State University of New York, Brooklyn, N.Y. For preparation of the cell bank system, see Example 1. For fermentation, harvesting and purification of the polysaccharide, see Example 1, except that during purification, the 30 kDa MWCO concentration step, prior to the chromatography step, is omitted.

Example 8 Preparation of Serotype 6A Pneumococcal Saccharide—CRM₁₉₇ Conjugate Activation and Conjugation

Serotype 6A polysaccharide is a high molecular weight polymer that had to be reduced in size prior to oxidation. Containers of serotype 6A saccharide were thawed and combined in a reaction vessel. To the vessel, 2 M acetic acid was added to a final concentration of 0.1 M for hydrolysis for 1.5 hours at 60° C. The reaction was cooled to 23° C. and neutralization was performed by adjusting the reaction mixture with 1 M NaOH to pH 6. Oxidation in the presence of sodium periodate was performed by incubation at 23° C. for 14-22 hours.

The activation reaction mixture was concentrated and diafiltered 10× with WFI using a 100K MWCO membrane. The retentate was filtered through a 0.2 μm filter.

Serotype 6A was compounded with sucrose and filled into 100 mL glass lyophilization bottles (50 mL target fill) and shell-frozen at −75° C. and lyophilized.

Bottles of lyophilized material were brought to room temperature and resuspended in dimethylsulfoxide (DMSO) at a saccharide/protein ratio of 1:1. After addition of sodium cyanoborohydride, the reaction mixture was incubated at 23° C. for 18 hours. Following the cyanoborohydride incubation, the reaction mixture was diluted with cold saline. Unreacted aldehydes were quenched by addition of sodium borohydride by incubation at 23° C. for 3-20 hours.

The diluted reaction mixture was transferred through a 5 μm prefilter into a retentate vessel. The reaction mixture was diafiltered 10× with 0.9% NaCl and 30× with succinate-buffered NaCl. The retentate was filtered through a 0.2 μm filter.

The conjugate solution was diluted to a saccharide target of 0.5 mg/mL, and then sterile filtered into FBC containers in a Class 100 hood. The conjugate was stored at 2-8° C.

For the characterization of the conjugate, see Example 2.

Example 9 Preparation of S. Pneumoniae Capsular Polysaccharide Serotype 7F

S. pneumoniae serotype 7F was obtained from Dr. Gerald Schiffman of the State University of New York, Brooklyn, N.Y. For preparation of the cell bank system, and for fermentation and harvesting of the polysaccharide, see Example 3. For an alternate fermentation and harvesting process, see the alternate process described in Example 1.

Purification

The purification of the pneumococcal polysaccharide consisted of several concentration/diafiltration operations, precipitation/elution, column chromatography, and depth filtration steps. All procedures were performed at room temperature unless otherwise specified.

Clarified broth from fermentor cultures of S. pneumoniae serotype 7F were concentrated and diafiltered using a 100 kDa MWCO filter. Diafiltration was accomplished using sodium phosphate buffer at neutral pH. Diafiltration removed the low molecular weight medium components from the higher molecular weight biopolymers such as nucleic acid, protein and polysaccharide.

Serotype 7F does not form a precipitate with HB. Instead, impurities were precipitated from the concentrated and diafiltered solution by adding the HB from a stock solution to a final concentration of 1% HB. The precipitate was captured on a depth filter and the filter was discarded. The polysaccharide was contained in the filtrate.

Sodium iodide (NaI) was added to the polysaccharide solution from a stock NaI solution to achieve a final concentration of 0.5% to precipitate HB. The precipitate was removed by depth filtration. The filtrate contained the target polysaccharide. The precipitation vessel and the filter were rinsed with a NaCl/NaI solution and the rinses were combined with the partially purified polysaccharide solution. The filter was discarded. The polysaccharide was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and diafiltered with a sodium chloride solution.

The partially purified polysaccharide solution was further purified by filtration through a depth filter impregnated with activated carbon. After filtration, the carbon filter was rinsed with a sodium chloride solution. The rinse was combined with the polysaccharide solution, which was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and adjusted with a 1M sodium phosphate buffer to achieve a final concentration of 0.025M sodium phosphate. The pH was checked and adjusted to 7.0±0.2.

The ceramic hydroxyapatite (HA) column was equilibrated with sodium phosphate buffer containing sodium chloride to obtain the appropriate conductivity (15 μS). The polysaccharide solution was then loaded onto the column. Under these conditions, impurities bound to the resin and the polysaccharide was recovered in the flow-through from the column. The polysaccharide was flushed through the column with buffer and was filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated using a 30 kDa MWCO filter. The concentrate was then diafiltered with WFI.

The diafiltered polysaccharide solution was filtered through a 0.2 μm membrane filter into stainless steel containers. Samples were removed for release testing and the purified polysaccharide was stored at 2°-8° C.

For characterization of the polysaccharide, see Example 3.

Example 10 Preparation of Serotype 7F Pneumococcal Saccharide—CRM₁₉₇ Conjugate Activation and Conjugation

Oxidation in the presence of sodium periodate was performed by incubation for 16-24 hrs at 23° C.

The activation reaction mixture was concentrated and diafiltered 10× with 10 mM NaOAc, pH 4.5, using a 100K MWCO membrane. The retentate was filtered through a 0.2 μm filter.

Serotype 7F was filled into 100 mL glass lyophilization bottles (50 mL target fill) and shell-frozen at −75° C. and lyophilized.

Bottles of lyophilized serotype 7F and CRM₁₉₇ were brought to room temperature and resuspended in DMSO at a saccharide/protein ratio of 1.5:1. After the addition of sodium cyanoborohydride, the reaction was incubated at 23° C. for 8-10 hours. Unreacted aldehydes were quenched by the addition of sodium borohydride by incubation at 23° C. for 16 hours.

The reaction mixture was diluted 10-fold with cold saline and transferred through a 5 μm prefilter into a retentate vessel. The reaction mixture was diafiltered 10× with 0.9% saline and 30× with succinate-buffered saline. The retentate was filtered through a 0.2 μm filter.

The conjugate solution was diluted to a saccharide target of 0.5 mg/mL 0.9% saline, and then sterile filtered into FBC containers in a Class 100 hood. The conjugate was stored at 2-8° C.

For characterization of the conjugate, see Example 4.

Example 11 Preparation of S. Pneumoniae Capsular Polysaccharide Serotype 19A

S. pneumoniae serotype 19A was obtained from Dr. Gerald Schiffman of the State University of New York, Brooklyn, N.Y. For preparation of the cell bank system, see Example 1. For fermentation, harvesting and purification of the polysaccharide, see Example 7. For characterization, see Example 3.

Example 12 Preparation of Serotype 19A Pneumococcal Saccharide—CRM₁₉₇ Conjugate Activation and Conjugation

Containers of serotype 19A saccharide were thawed and combined in a reaction vessel. Sodium acetate was added to 10 mM (pH 5.0) and oxidation was carried out in the presence of sodium periodate by incubation for 16-24 hrs at 23° C.

The activation reaction mixture was concentrated and diafiltered 10× with 10 mM acetate, pH 5.0, using a 100K MWCO membrane. The retentate was filtered through a 0.2 μm filter.

The activated saccharide was compounded with sucrose followed by the addition of CRM₁₉₇. The serotype 19A activated saccharide and CRM₁₉₇ mixture (0.8:1 ratio) was filled into 100 mL glass lyophilization bottles (50 mL target fill) and shell-frozen at −75° C. and lyophilized.

Bottles of lyophilized material were brought to room temperature and resuspended in DMSO. To the saccharide/protein mixture, sodium cyanoborohydride (100 mg/ml) was added. The reaction was incubated at 23° C. for 15 hours. Following the cyanoborohydride incubation, unreacted aldehydes were quenched by the addition of sodium borohydride by incubation at 23° C. for 3-20 hours.

The reaction mixture was diluted 10-fold with cold saline and transferred through a 5 μm prefilter into a retentate vessel. The reaction mixture was diafiltered 10× with 0.9% NaCl, 0.45-μm filtered, and 30× with diafiltration using 5 mM succinate/0.9% NaCl buffer, pH 6. The retentate was filtered through a 0.2 μm filter.

The conjugate solution was diluted to a target of 0.5 mg/mL using 5 mM succinate/0.9% saline, and then sterile filtered into FBC containers in a Class 100 hood. The conjugate was stored at 2-8° C.

For characterization of the conjugate, see Example 4.

Example 13 Preparation of S. Pneumoniae Capsular Polysaccharide Serotypes 4, 6B, 9V, 14, 18C, 19F and 23F Preparation of the S. Pneumoniae Seed Culture

S. pneumoniae serotypes 4, 6B, 9V, 18C, 19F and 23F were obtained from Dr. Gerald Schiffman, State University of New York, Brooklyn, N.Y. S. pneumoniae serotype 14 was obtained from the ATCC, strain 6314.

Separately, one vial of each of the desired serotypes of Streptococcus pneumoniae was used to start a fermentation batch. Two bottles containing a soy-based medium and phenol red were adjusted to a pH range of 7.4±0.2 using sodium carbonate, and the required volume of 50% dextrose/1% magnesium sulfate solution was then added to the bottles. The two bottles were inoculated with different amounts of seed. The bottles were incubated at 36°±2° C. until the medium turned yellow. Following incubation, samples were removed from each bottle and tested for optical density (OD) (0.3 to 0.9) and pH (4.6 to 5.5). One of the two bottles was selected for inoculation of the seed fermentor.

Soy-based medium was transferred to the seed fermentor and sterilized. Then a volume of 50% dextrose/1% magnesium sulfate solution was added to the fermentor. The pH and agitation of the seed fermentor were monitored and controlled (pH 6.7 to 7.4). The temperature was maintained at 36°±2° C. The seed inoculum (bottle) was aseptically connected to the seed fermentor and the inoculum was transferred. The fermentor was maintained in pH control and samples were periodically removed and tested for OD and pH. When the desired OD of 0.5 at 600 nm was reached, the intermediate fermentor was inoculated with the fermentation broth from the seed fermentor.

Soy-based medium was transferred to the intermediate fermentor and sterilized. Then a volume of 50% dextrose/1% magnesium sulfate solution was added to the fermentor. The pH and agitation of the intermediate fermentor were monitored and controlled (pH 6.7 to 7.4). The temperature was maintained at 36°±2° C. The contents of the seed fermentor were transferred to the intermediate fermentor. The fermentor was maintained in pH control and samples were periodically removed and tested for OD and pH. When the desired OD of 0.5 at 600 nm was reached, the production fermentor was inoculated with the fermentation broth from the intermediate fermentor.

Soy-based medium was transferred to the production fermentor and sterilized. Then a volume of 50% dextrose/1% magnesium sulfate solution was added to the fermentor. The pH and agitation of the production fermentor were monitored and controlled (pH 6.7 to 7.4). The temperature was maintained at 36°±2° C. The fermentor was maintained in pH control and samples were periodically removed and tested for OD and pH, until the fermentation was complete.

Deoxycholate sodium was added to the fermentor to a final concentration of approximately 0.12% w/v. The culture was mixed for a minimum of thirty minutes and the temperature set point was reduced to 10° C. The culture was incubated overnight and following confirmation of inactivation, the pH of the culture was adjusted to between 6.4 and 6.8, as necessary, with 50% acetic acid. The temperature of the fermentor was increased to 20°±5° C. and the contents were transferred to the clarification hold tank.

The contents of the clarification hold tank (including the cellular debris) were processed through a centrifuge at a flow rate between 25 and 600 liters per hour (except Serotype 4, wherein the cell debris was discarded and the flow rate tightened to between 25 and 250 liters per hour). Samples of the supernatant were removed and tested for OD. The desired OD during the centrifugation was ≦0.15.

Initially, the supernatant was recirculated through a depth filter assembly until an OD of 0.05±0.03 was achieved. Then the supernatant was passed through the depth filter assembly and through a 0.45 μm membrane filter to the filtrate hold tank.

Subsequently, the product was transferred through closed pipes to the purification area for processing.

All of the above operations (centrifugation, filtration and transfer) were performed between 10° C. to 30° C.

For an alternate fermentation and harvesting process for serotypes 4 and 6B, see the alternate process described in Example 1.

Purification

The purification of each pneumococcal polysaccharide consisted of several concentration/diafiltration operations, precipitation/elution, column chromatography, and depth filtration steps. All procedures were performed at room temperature unless otherwise specified.

Clarified broth from the fermentor cultures of the desired S. pneumoniae serotype was concentrated and diafiltered using a 100 kDa MWCO filter. Diafiltration was accomplished using sodium phosphate buffer at pH<9.0. Diafiltration removed the low molecular weight medium components from the higher molecular weight biopolymers such as nucleic acid, protein and polysaccharide.

The polysaccharide was precipitated from the concentrated and diafiltered solution by adding HB from a stock solution to give a final concentration of 1% HB (w/v) (except Serotype 23F, which had a final concentration of 2.5%). The polysaccharide/HB precipitate was captured on a depth filter and the filtrate was discarded. (Note: Serotype 14 does not precipitate; therefore the filtrate was retained.) The polysaccharide precipitate was resolubilized and eluted by recirculating a sodium chloride solution through the precipitate-containing depth filter. The filters were then rinsed with additional sodium chloride solution.

Sodium iodide (NaI) was added to the polysaccharide solution from a stock NaI solution to achieve a final concentration of 0.5% to precipitate HB (except for Serotype 6B, which had a final concentration of 0.25%). The precipitate was removed by depth filtration. The filtrate contained the target polysaccharide. The filter was discarded. The polysaccharide was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and diafiltered with a sodium chloride solution.

The partially purified polysaccharide solution was further purified by filtration through a depth filter impregnated with activated carbon. After filtration, the carbon filter was rinsed with a sodium chloride solution. The rinse was combined with the polysaccharide solution, which was then filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated on a 30 kDa MWCO ultrafilter and the filter was rinsed with a sodium chloride solution. The pH was checked and adjusted to 7.0±0.3.

The ceramic hydroxyapatite (HA) column was equilibrated with sodium phosphate buffer containing sodium chloride until the pH is 7.0±0.3 and the conductivity was 26±4 μS. The polysaccharide solution was then loaded onto the column. Under these conditions, impurities bound to the resin and the polysaccharide was recovered in the flow through from the column. The polysaccharide solution was filtered through a 0.2 μm filter.

The polysaccharide solution was concentrated using a 30 kDa MWCO filter. The concentrate was then diafiltered with WFI until the conductivity was <15 μS.

The diafiltered polysaccharide solution was filtered through a 0.2 μm membrane filter into bulk containers and stored at 2-8° C.

Example 14 Preparation of Pneumococcal Saccharide—CRM₁₉₇ Conjugates For Serotypes 4, 6B, 9V, 14, 18C, 19F and 23F Activation Process

The different serotype saccharides follow different pathways for activation (hydrolysis or no hydrolysis prior to activation) and conjugation (aqueous or DMSO reactions) as described in this example.

Polysaccharide was transferred from the bulk containers to the reactor vessel. The polysaccharide was then diluted in WFI and sodium phosphate to a final concentration range of 1.6-2.4 mg/mL.

Step 1.

For serotypes 6B, 9V, 14, 19F and 23F, pH was adjusted to pH 6.0±0.3.

For serotype 4, hydrochloric acid (0.01 M final acid concentration) was added and the solution was incubated for 25-35 minutes at 45°±2° C. Hydrolysis was stopped by cooling to 21-25° C. and adding 1M sodium phosphate to a target of pH 6.7±0.2. An in-process test was done to confirm an appropriate level of depyruvylation.

For serotype 18C, glacial acetic acid (0.2 M final acid concentration) was added and the solution was incubated for 205-215 minutes at 94°±2° C. Temperature was then decreased to 21-25° C. and 1-2 M sodium phosphate was added to a target of pH 6.8±0.2.

Step 2: Periodate Reaction

The required sodium periodate molar equivalents for pneumococcal saccharide activation was determined using total saccharide content (except for serotype 4). For serotype 4, a ratio of 0.8-1.2 moles of sodium periodate per mole of saccharide was used. With thorough mixing, the oxidation reaction was allowed to proceed between 16 to 20 hours at 21-25° C. for all serotypes except 19F for which the temperature was ≦15° C.

Step 3: Ultrafiltration

The oxidized saccharide was concentrated and diafiltered with WFI (0.01 M sodium phosphate buffer pH 6.0 for serotype 19F) on a 100 kDa MWCO ultrafilter (5 kDa ultrafilter for 18C). The permeate was discarded and the retentate was filtered through a 0.22 μm filter.

Step 4: Lyophilization

For serotypes 4, 9V, and 14 the concentrated saccharide was mixed with CRM₁₉₇ carrier protein, filled into glass bottles, shell-frozen and stored at ≦−65° C. The frozen concentrated saccharide-CRM₁₉₇ was lyophilized and then stored at −25°±5° C.

For serotypes 6B, 19F, and 23F a specified amount of sucrose was added which was calculated to achieve a 5%±3% sucrose concentration in the conjugation reaction mixture. Serotype 18C did not require sucrose addition. The concentrated saccharide was then filled into glass bottles, shell-frozen and stored at ≦−65° C. The frozen concentrated saccharide was lyophilized and then stored at −25°±5° C.

Conjugation Process

Two conjugation processes were used: aqueous conjugation for serotypes 4, 9V, 14 and 18C, and DMSO conjugation for serotypes 6B, 19F and 23F.

Aqueous Conjugation

Step 1: Dissolution

For serotypes 4, 9V and 14, the lyophilized activated saccharide-CRM₁₉₇ mixture was thawed and equilibrated at room temperature. The lyophilized activated saccharide-CRM₁₉₇ was then reconstituted in 0.1M sodium phosphate buffer at a typical ratio of:

1 L of buffer per 16-24 g of saccharide for serotype 4 and 9V

1 L of buffer per 6-10 g of saccharide for serotype 14

The reaction mixture was incubated at 37°±2° C. until total dissolution for the serotype 9V and at 23°±2° C. for serotypes 4 and 14.

For serotype 18C, the lyophilized saccharide was reconstituted in a solution of CRM₁₉₇ in 1M dibasic sodium phosphate at a typical ratio of 0.11 L of sodium phosphate per 1 L of CRM₁₉₇ solution. The reaction mixture (8-12 g/L saccharide concentration) was incubated at 23°±2° C. until total dissolution.

The pH was tested as an in-process control at this stage.

Step 2: Conjugation Reaction

For serotypes 4 and 9V, the conjugation reaction was initiated by adding the sodium cyanoborohydride solution (100 mg/mL) to achieve 1.0-1.4 moles sodium cyanoborohydride per mole of saccharide. The reaction mixture was incubated for 44-52 hours at 37±2° C. The temperature was then reduced to 23°±2° C. and sodium chloride 0.9% was added to the reactor. Sodium borohydride solution (100 mg/mL) was added to achieve 1.8-2.2 molar equivalents of sodium borohydride per mole saccharide. The mixture was incubated for 3-6 hours at 23°±2° C. The mixture was diluted with sodium chloride 0.9% and the reactor was rinsed. The diluted conjugation mixture was filtered using a 1.2 μm pre-filter into a holding vessel.

For serotypes 14 and 18C, the conjugation reaction was initiated by adding the cyanoborohydride solution (100 mg/mL) to achieve 1.0-1.4 moles of sodium cyanoborohydride per mole of saccharide. The reaction mixture was incubated for 12-24 hours at 23°±2° C. The temperature was increased to 37°±2° C. and the reaction was incubated for 72-96 hours. The temperature was then reduced to 23°±2° C. and 0.9% sodium chloride was added to the reactor. Sodium borohydride solution (100 mg/mL) was added to achieve 1.8-2.2 molar equivalents of sodium borohydride per mole of saccharide. The mixture was incubated for 3-6 hours at 23°±2° C. The mixture was diluted with 0.9% sodium chloride and the reactor was rinsed. The diluted conjugation mixture was then filtered using a 1.2 μm pre-filter into a holding vessel.

Step 3: Ultrafiltration 100 kDa

The diluted conjugation mixture was concentrated and diafiltrated on a 100 kDa MWCO ultrafilter with either a minimum of 15 volumes (serotype 4) or 40 volumes (serotypes 9V, 14, and 18C) of 0.9% sodium chloride.

The permeate was discarded.

For serotype 4, the retentate was filtered through a 0.45 μm filter.

An in-process control (saccharide content) was performed at this step.

Step 4: HA Column Purification

This step was only performed for the serotype 4 conjugate.

The HA column was first neutralized using 0.5M sodium phosphate buffer (pH 7.0±0.3) and then equilibrated with 0.9% sodium chloride. The filtered retentate (serotype 4) was loaded onto the column at a flow rate of 1.0 L/min. The column washed with 0.9% sodium chloride at a flow rate of ≦2.0 L/min. The product was then eluted with 0.5M sodium phosphate buffer at a flow rate of ≦2.0 L/min.

The HA fraction was then concentrated and diafiltered on a 100 kDa MWCO membrane with a minimum of 20 volumes of 0.9% sodium chloride. The permeate was discarded.

Step 5: Sterile Filtration

The retentate after the 100 kDa MWCO diafiltration was filtered through a 0.22 μm filter. In-process controls (saccharide content, free protein, free saccharide and cyamide) were performed on the filtered product. In-process controls on filtered retentate were performed to determine whether additional concentration, diafiltration, and/or dilution were needed to meet FBC targets. These and additional tests were repeated in FBC samples.

As necessary, the filtered conjugate was diluted with 0.9% sodium chloride in order to achieve a final concentration of less than 0.55 g/L. Release tests for saccharide content, protein content and saccharide:protein ratio were performed at this stage.

Finally, the conjugate was filtered (0.22 μm) and filled into 10 L stainless steel canisters at a typical quantity of 2.64 g/canister. At this stage, yield, saccharide content, protein content, pH, saccharide:protein ratio and lysine content were performed as in-process controls. Release testing (appearance, free protein, free saccharide, endotoxin, molecular size determination, residual cyamide, saccharide identity, CRM₁₉₇ identity) was performed at this stage.

DMSO Conjugation

Step I: Dissolution

The lyophilized activated saccharide serotypes 6B, 19F, 23F and the lyophilized CRM₁₉₇ carrier protein were equilibrated at room temperature and reconstituted in DMSO. The dissolution concentration typically ranged from 2-3 grams of saccharide (2-2.5 g protein) per liter of DMSO.

Step II: Conjugation Reaction

The activated saccharide and CRM₁₉₇ carrier protein were mixed for 60-75 minutes at 23°2° C. at a ratio range of 0.6 g-1.0 g saccharide/g CRM₁₉₇ for serotypes 6B and 19F or 1.2 to 1.8 g saccharide/g CRM₁₉₇ for serotype 23F.

The conjugation reaction was initiated by adding the sodium cyanoborohydride solution (100 mg/mL) at a ratio of 0.8-1.2 molar equivalents of sodium cyanoborohydride to one mole activated saccharide. WFI was added to the reaction mixture to a target of 1% (v/v) and the mixture was incubated for over 40 hours at 23°±2° C.

Sodium borohydride solution, 100 mg/mL (typical 1.8-2.2 molar equivalents sodium borohydride per mole activated saccharide) and WFI (target 5% v/v) were added to the reaction and the mixture was incubated for 3-6 hours at 23°±2° C. This procedure reduced any unreacted aldehydes present on the saccharides. Then the reaction mixture was transferred to a dilution tank containing 0.9% sodium chloride at <15° C.

Step III: 100 kDa Ultrafiltration

The diluted conjugate mixture was filtered through a 1.2 μm filter and concentrated and diafiltered on a 100 kDa MWCO membrane with a minimum of 15 volumes of 0.9% sodium chloride (0.01M sodium phosphate/0.05M NaCl buffer was used for serotype 23F). The permeate was discarded. The retentate was filtered through a 0.45 μm filter. An in-process saccharide content sample was taken at this stage.

Step IV: DEAE Column Purification

This step was only performed for serotype 23F.

The DEAE column was equilibrated with 0.01M sodium phosphate/0.05M sodium chloride buffer. The filtered retentate (serotype 23F) was loaded onto the column and washed with 0.01M sodium phosphate/0.05M sodium chloride buffer. The column was then washed with 0.01M sodium phosphate/0.9% NaCl buffer. The product was then eluted with 0.01M sodium phosphate/0.5M sodium chloride buffer.

Step V: 100 kDa Ultrafiltration

The retentate from 6B and 19F was concentrated and diafiltered with at least 30 volumes of 0.9% sodium chloride. The permeate was discarded.

The eluate from serotype 23F was concentrated and diafiltered with a minimum of 20 volumes of 0.9% sodium chloride. The permeate was discarded.

Step VI: Sterile Filtration

The retentate after the 100 kDa MWCO diafiltration was filtered through 0.22 μm filter. In-process controls (saccharide content, free protein, free saccharide, residual DMSO and residual cyamide) were performed on the filtered product. In-process controls on filtered retentate were performed to determine whether additional concentration, diafiltration, and/or dilution were needed to meet FBC targets. These and additional tests were repeated in FBC samples.

As necessary, the filtered conjugate was diluted with 0.9% sodium chloride to achieve a final concentration of less than 0.55 g/L. Release tests for saccharide content, protein content and saccharide:protein ratio were performed at this stage.

Finally, the conjugate was filtered (0.22 μm) and filled into 10 L stainless steel canisters at a quantity of 2.64 g/canister. At this stage, yield, saccharide content, protein content, pH, saccharide:protein ratio and lysine content were performed as in-process controls. Release testing (appearance, free protein, free saccharide, endotoxin, molecular size determination, residual cyamide, residual DMSO, saccharide identity and CRM₁₉₇ identity) was performed at this stage.

Example 15 Formulation of a Multivalent Pneumococcal Conjugate Vaccine

The final bulk concentrates of the 13 conjugates contain 0.85% sodium chloride. Type 3, 6A, 7F and 19A bulk concentrates also contain 5 mM sodium succinate buffer at pH 5.8. The required volumes of bulk concentrates were calculated based on the batch volume and the bulk saccharide concentrations. After 80% of the 0.85% sodium chloride (physiological saline) and the required amount of succinate buffer were added to the pre-labeled formulation vessel, bulk concentrates were added. The preparation was then sterile filtered through a 0.22 μm membrane into a second container by using a Millipore Durapore membrane filter unit. The first container washed with the remaining 20% of 0.85% sodium chloride and the solution was passed through the same filter and collected into the second container. The formulated bulk was mixed gently during and following the addition of bulk aluminum phosphate. The pH was checked and adjusted if necessary. The formulated bulk product was stored at 2-8° C.

The formulated bulk product was filled into Type 1 borosilicate glass syringes obtained from Becton Dickinson. The vaccine was monitored at regular intervals for turbidity to ensure the uniformity of the filling operation. The filled vaccine (Final Product) was stored at 2-8° C.

Example 16 Immunogenicity of the 13-Valent Conjugate Vaccine

To date, the preclinical studies performed on the 13vPnC vaccine have been in rabbits. Studies #HT01-0021 and #HT01-0036 were designed to independently examine the effect of chemical conjugation of capsular polysaccharides (PSs) from S. pneumoniae to CRM₁₉₇ and the effect of aluminum phosphate (AIPO₄) adjuvant on the immune response to the 13vPnC vaccine in rabbits. These effects were characterized by antigen-specific ELISA for serum IgG concentrations and for antibody function by opsonophagocytic assay (OPA).

Study #HT01-0021

Study #HT01-0021 examined the ability of the 13vPnC vaccine with AIPO₄ adjuvant to elicit vaccine serotype-specific immune responses. The pneumococcal serotypes represented in the 13vPnC vaccine include types 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F. Secondary objectives included an evaluation of the kinetics and duration of the antibody response. New Zealand White rabbits were immunized intramuscularly at week 0 and week 2 with the planned human clinical dose of each polysaccharide (2 μg of each PS, except 4 μg of 6B) formulated with or without AIPO₄ (100 μg/dose). Sera were collected at various time points. Serotype specific IgG was measured by ELISA and functional activity was assessed by OPA.

Table 4 shows the geometric mean titer (GMT) achieved in pooled serum samples, following two doses of the 13vPnC vaccine. A ratio of the IgG GMTs was used to compare responses from week 4 to week 0. These data demonstrate that the inclusion of AIPO₄ in the 13vPnC formulation elicited higher levels of IgG antibody in comparison to the same vaccine without adjuvant. Although the antibody responses were greater when AIPO₄ was included in the formulation, these increases were not statistically significant.

Functional antibody responses were also assessed in rabbits following immunization with the two 13vPnC formulations (Table 5). When comparing vaccine formulations with or without adjuvant, higher OPA GMTs were observed in the 13vPnC+AIPO₄ vaccine treatment group. OPA titers were detected in week 4 serum pools to all vaccine serotypes in both groups. For the majority of the serotypes, OPA titers measured at week 4 were at least 4-fold higher than those at week 0 (baseline).

The kinetic responses to each of the 13vPnC vaccine serotypes were evaluated from serum pools of both treatment groups. IgG titers to each serotype were measured from blood draws at week 0 and weeks 1, 2, 3, 4, 8, 12, 26, and 39 and then compared. With the exception of serotype 1, antibody responses in animals receiving adjuvanted vaccine were superior to those that received non-adjuvanted vaccine and peaked at week 2 of the immunization schedule (data not shown).

Overall, the data indicate that the 13vPnC vaccine formulated with aluminum phosphate is immunogenic in rabbits, eliciting substantial antibody responses to the pneumococcal capsular polysaccharides contained in the vaccine and these responses are associated with functional activity. The responses observed to the seven core serotypes following immunization with 13vPnC+AIPO₄ are consistent with historical responses of rabbits to the heptavalent formulation. TABLE 4 Rabbit IgG Immune Responses (GMTs) Following Immunization with Two Doses of 13-valent Pneumococcal Glycoconjugate Diluent with ALPO₄ ^(a) 13vPnC^(a) 13vPnC + ALPO₄ ^(a) Ratio Week 4 Ratio Week 4 Ratio Serotype Week 0 Week 4 Wk 4:Wk 0 Week 0 (95% Cl) Wk 4:Wk 0 Week 0 (95% Cl) Wk 4:Wk 0  1 <100 <100 1.0 50  5,926 119 50 11,091 222  (2,758-12,733)  (5,327-23,093)  3 <100 <100 1.0 50  6,647 133 58 16,443 284  (2,773-15,932)  (7,096-38,106)  4 <100 <100 1.0 50 13,554 271 50 29,183 584  (8,031-22,875) (15,342-55,508)  5 134 <100 0.4 50  5,859 117 50 16,714 334  (2,450-14,009)  (6,959-40,140)  6A 141 <100 0.4 74 22,415 303 83 63,734 768 (11,987-41,914)  (21,141-192,146)  6B <100 <100 1.0 57  8,108 142 54 23,505 435  (3,564-18,444) (11,286-48,955)  7F 3,859 579 0.2 171 43,591 444 143 84,888 496 (26,931-70,557)  (46,445-155,151)  9V 289 995 3.4 205 15,780 125 208  43,331^(b) 217  (7,193-34,616) (23,256-71,510) 14 437 177 0.4 61  6,906 113 70 16,076 322  (3,416-13,962)  (9,649-26,785) 18C <100 <100 1.0 50 21,283 426 50 35,040 701 (15,770-28,725) (24,708-49,692) 19A <100 <100 1.0 121 113,599  939 144 280,976  1,951  (54,518-236,707) (119,587-660,167) 19F <100 <100 1.0 50 14,365 287 50 24,912 498  (7,346-28,090)  (9,243-67,141) 23F <100 <100 1.0 50  5,323 106 50 15,041 301  (1,894-14,962)  (4,711-48,018) ^(a)GMTs of pooled sera consisted of equal volumes of serum from each individual rabbit within a group ^(b)Statistically different (p = 0.022) from treatment group without ALPO₄

TABLE 5 S. pneumoniae OPA GMTs for NZW Rabbit Serum Pools Following Immunization with Two Doses of 13-valent Pneumococcal Glycoconjugate 13vPnC^(a) 13vPnC + ALPO₄ ^(a) Sero- Ratio Ratio type Week 0 Week 4 Wk 4:Wk 0 Week 0 Week 4 Wk 4:Wk 0  1 <8 64 16 <8 64 16  3 <8 8 2 <8 16 4  4 <8 16 4 <8 32 8  5 <8 128 32 <8 512 128  6A 8 128 16 8 512 64  6B <8 256 64 8 1,024 128  7F 8 64 8 8 128 16  9V 8 64 8 8 128 16 14 16 32 2 16 32 2 18C 8 256 32 <8 256 64 19A <8 256 64 <8 1,024 256 19F <8 128 32 <8 512 128 23F 8 64 8 <8 256 64 ^(a)Pools consisted of equal volumes of serum from individual rabbits within a treatment group (n = 12) Study #HT01-0036

Study #HT01-0036 compared rabbit immune responses to the polysaccharides (PSs) contained in the vaccine, after immunization with the 13vPnC vaccine with or without conjugation to the CRM₁₉₇ protein. New Zealand White rabbits were immunized intramuscularly at week 0 and week 2 with a dose of 2.2 μg of each PS (except 4.4 μg of 6B). Animals received one of three vaccine preparations: (a) 13vPnC (PS directly conjugated to CRM₁₉₇), (b) 13vPnPS, (free PS) or (c) 13vPnPS+CRM₁₉₇ (free PS mixed with CRM₁₉₇). All vaccine preparations contained AIPO₄ as the adjuvant at 125 μg/dose.

Serotype specific immune responses for all vaccine preparations were evaluated in an IgG ELISA and complement-mediated OPA measuring functional antibody. The immune responses were compared between the treatment groups.

Table 6 presents GMT data obtained from week 4 bleeds analyzed in antigen specific IgG ELISAs. Additional analyses show the ratio of GMT values at week 4 to week 0. The data indicate that the conjugate vaccine preparation elicited greater serum IgG titers than free PS or free PS+CRM₁₉₇ vaccine. With the exception of S. pneumoniae type 14, the 13vPnC vaccine was able to induce functional antibodies to the representative strains of S. pneumoniae in an OPA (Table 7). After two immunizations with either the 13vPnPS or 13vPnPS+CRM₁₉₇ vaccine, neither could induce OPA titers ≧8-fold at week 4 relative to week 0 for 10 out of the 13 serotypes measured (Table 7).

In conclusion, these results indicate that conjugation of the 13-valent pneumococcal vaccine polysaccharides produces higher serum IgG titers and overall greater functional antibody activity than seen with free polysaccharide alone or mixed with unconjugated CRM₁₉₇. TABLE 6 Rabbit IgG Responses (GMTs) to PnPS by ELISA Following Immunization with Two Doses of 13-valent Pneumococcal Glycoconjugate 13vPnPS = CRM₁₉₇ 13vPnPS (free (PS mixed with PS) CRM₁₉₇) 13vPnC Week 4 Ratio Week 4 Ratio Week 4 Ratio Serotype Week 0 (95% Cl) Wk 4:Wk 0 Week 0 (95% Cl) Wk 4:Wk 0 Week 0 (95% Cl) Wk 4:Wk 0  1 378 2,290   5.8 395 1,959   5.0 472 35,970 76.2   (843-5,790)   (809-4,739) (29,130-44,417)  3 57 240 4.2 89 163 1.8 50 10,414 208.3  (64-908)  (74-358) (10,414-16,676)  4 50 379 7.6 50 607 12.1 50 12,890 257.8 (150-959)   (313-1,178)  (9,117-18,224)  5 343 226 4.5 50 321 6.4 50 35,264 705.3 (113-450) (147-701) (24,467-50,824)  6A 154 466 3.0 98 210 2.1 163 234,245  1,437.1 (316-688)  (95-464) (167,152-328,283)  6B 63 727 11.6 62 745 12.0 131 33,599 256.5   (384-1,375)   (384-1,440) (22,934-49,222)  7F 50  61 1.2 50  72 1.4 50 35,702 714.0 (39-95)  (47-111) (24,350-52,347)  9V 50 104 2.0 55 169 3.0 50 50,033 1,000.7  (48-195)  (74-390) (34,765-72,007) 14 66 298 4.5 50 195 3.9 50 20,121 402.4 (117-757)  (71-535) (12,087-32,138) 18C 89 1,555   17.5 66 761 11.5 101 71,451 707.4   (655-3,688)   (300-1,935)  (32,745-124,641) 19A 50  89 1.8 50  80 1.6 50 23,485 469.7  (44-179)  (39-163) (12,857-42,723) 19F 61 1,362   22.3 61 991 16.3 67 19,358 288.9   (559-3,317)   (370-2,654) (12,553-33,173) 23F 73 1,085   14.9 121 638 5.3 68 45,972 676.1   (487-2,420)   (311-1,311) (25,134-84,089)

TABLE 7 S. pneumoniae OPA Titers for Rabbit Serum Pools Following Immunization with Two Doses of 13-valent Pneumococcal Vaccines OPA Titers 13vPnPS + CRM₁₉₇ (free PS 13vPnPS mixed with No (free PS) CRM₁₉₇) 13vPnC Treatment Ratio Ratio Ratio Serotype Week 0^(a) Week 4 Wk 4:Wk 0 Week 4 Wk 4:Wk 0 Week 4 Wk 4:Wk 0  1 4 16 4 16 4 8 32  3 4 4 1 4 1 4 8  4 4 4 1 4 1 4 64  5 4 32 8 16 4 16 64  6A 8 64 8 32 4 32 664  6B 8 64 8 32 4 32 32  7F 16 32 2 16 1 16 16  9V 16 16 1 32 2 32 8 14 16 16 1 16 1 16 2 18C 4 16 4 16 4 8 64 19A 8 8 1 8 1 16 64 19F 4 4 1 4 1 8 64 23F 16 32 2 16 1 32 32 ^(a)Used as week 0 values for all groups

Example 17 Alternate Procedure for Serotype 3 Pneumococcal Saccharide—CRM₁₉₇ Conjugation

Containers of purified polysaccharide were thawed and combined in a reaction vessel and heated to a temperature of 85° C. When the temperature of the mixture reached approximately 35° C. during temperature ramp-up, 2 M acetic acid was added to achieve a 0.1 M acetic acid concentration. When the temperature of the mixture reached 85° C., it was maintained at this temperature for 1 hour to achieve hydrolysis/depolymerization. The hydrolyzed/depolymerized polysaccharide was cooled to 23° C. and 1 M MgCl₂ was added to achieve a 0.1 M MgCl₂ concentration. Oxidation was carried out using 1-1.25 mole equivalent of periodic acid, added as a 50 mg/mL solution in WFI. The mixture was incubated at 23° C. for 16-24 hours.

The reaction mixture was purified by diafiltration against 10× volumes of WFI using a 100K MWCO polyethersulfone (PES) membrane. The purified, activated polysaccharide was adjusted to a pH of 6.0 using 0.2 M phosphate buffer (pH 7.0), compounded with CRM₁₉₇ at a polysaccharide/protein ratio of 2:1, shell-frozen at −75° C., and co-lyophilized for 71 hours. Following co-lyophilization, the polysaccharide/CRM₁₉₇ mixture was stored at −25°±5° C. until conjugation. For conjugation, the co-lyophilized polysaccharide/CRM₁₉₇ mixture was dissolved in 0.1 M phosphate buffer at a concentration of 20 mg/mL polysaccharide and the pH was adjusted to 6.2 with a combination of 0.2 M phosphate buffer, pH 4.6, and 1 M NaOH, followed by the addition of 0.5 mole equivalent of sodium cyanoborohydride as a 100 mg/mL solution in 0.15 M phosphate buffer, pH 7.5. The reaction mixture was stirred and incubated at 37° C. for 44 hours. Following the cyanoborohydride incubation, the reaction mixture was diluted 1× with cold (2-8° C.) 0.9% saline followed by the addition of 1 mole equivalent of sodium borohydride as a 100 mg/mL solution in WFI to cap unreacted aldehydes at 23° C. for 3-6 hours.

The reaction mixture was transferred through a 0.45-5 μm prefilter into a retentate vessel and then purified by diafiltration using a 100K MWCO regenerated cellulose membrane. The reaction mixture was then diafiltered 30× against 0.1 M phosphate buffer, pH 9.0, and 20× against 0.15 M phosphate buffer, pH 6.0. A final 20× diafiltration was performed against 5 mM succinate/0.9% saline, pH 6.0. The diafiltered conjugate was filtered through a 0.2 μm filter and assayed for saccharide content. Based on saccharide analysis, the conjugate solution was diluted with 5 mM succinate/0.9% saline, pH 6.0, to a target of 0.5 mg/mL and again sterile filtered (0.2 μm) to give the final batch concentrate conjugate. The conjugate was stored at 2-8° C.

For characterization of the conjugate, see Example 4.

It should be understood that the foregoing discussion and examples merely present a detailed description of certain embodiments. It therefore should be apparent to those of ordinary skill in the art that various modifications and equivalents can be made without departing from the spirit and scope of the invention.

All journal articles, other references, patents and patent applications that are identified in this patent application are incorporated by reference in their entirety.

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1. A method for making an immunogenic conjugate comprising Streptococcus pneumoniae serotype 3 polysaccharide covalently linked to a carrier protein, the method comprising: (a) reacting purified serotype 3 polysaccharide with a mild acid resulting in a hydrolyzed serotype 3 polysaccharide; (b) reacting the hydrolyzed serotype 3 polysaccharide with an oxidizing agent in the presence of bivalent cations resulting in an activated serotype 3 polysaccharide; (c) compounding the activated serotype 3 polysaccharide with a carrier protein; (d) reacting the compounded, activated serotype 3 polysaccharide and carrier protein with a reducing agent resulting in a serotype 3 polysaccharide:carrier protein conjugate; and (e) capping unreacted aldehydes in the serotype 3 polysaccharide:carrier protein conjugate resulting in an immunogenic conjugate comprising Streptococcus pneumoniae serotype 3 polysaccharide covalently linked to a carrier protein.
 2. The method of claim 1, further comprising purifying the activated serotype 3 polysaccharide prior to compounding with the carrier protein.
 3. The method of claim 1, further comprising co-lyophilizing the compounded, activated serotype 3 polysaccharide and carrier protein prior to reacting with the reducing agent.
 4. The method of claim 1, further comprising purifying the immunogenic conjugate.
 5. The method of claim 1, wherein the mild acid is acetic acid.
 6. The method of claim 1, wherein the oxidizing agent is periodic acid and the bivalent cations are Mg²⁺.
 7. The method of claim 1, wherein the carrier protein is CRM₁₉₇.
 8. The method of claim 1, wherein the reducing agent is sodium cyanoborohydride.
 9. The method of claim 1, wherein capping unreacted aldehydes comprises reacting the serotype 3 polysaccharide:carrier protein conjugate with sodium borohydride.
 10. A method for making an immunogenic conjugate comprising Streptococcus pneumoniae serotype 3 polysaccharide covalently linked to a carrier protein, the method comprising: (a) reacting purified serotype 3 polysaccharide with acetic acid resulting in a hydrolyzed serotype 3 polysaccharide; (b) reacting the hydrolyzed serotype 3 polysaccharide with periodic acid in the presence of MgCl₂ resulting in an activated serotype 3 polysaccharide; (c) purifying the activated serotype 3 polysaccharide; (d) compounding the activated serotype 3 polysaccharide with a carrier protein; (e) co-lyophilizing the compounded, activated serotype 3 polysaccharide and carrier protein; (f) reacting the co-lyophilized, activated serotype 3 polysaccharide and carrier protein with sodium cyanoborohydride resulting in a serotype 3 polysaccharide:carrier protein conjugate; and (g) capping unreacted aldehydes in the serotype 3 polysaccharide:carrier protein conjugate with sodium borohydride resulting in an immunogenic conjugate comprising Streptococcus pneumoniae serotype 3 polysaccharide covalently linked to a carrier protein.
 11. The method of claim 10, further comprising purifying the immunogenic conjugate.
 12. The method of claim 10, wherein the carrier protein is CRM₁₉₇.
 13. A method for making an activated Streptococcus pneumoniae serotype 3 polysaccharide, the method comprising: (a) reacting purified serotype 3 polysaccharide with a mild acid resulting in a hydrolyzed serotype 3 polysaccharide; and (b) reacting the hydrolyzed serotype 3 polysaccharide with an oxidizing agent in the presence of bivalent cations resulting in an activated serotype 3 polysaccharide.
 14. The method of claim 13, further comprising purifying the activated serotype 3 polysaccharide following oxidation.
 15. The method of claim 13, wherein the mild acid is acetic acid.
 16. The method of claim 13, wherein the oxidizing agent is periodic acid and the bivalent cations are Mg²⁺. 